6  '77 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 
BUREAU  OF  ENTOMOLOGY— BULLETIN  NO.  77. 

L.  O.  HOWARD.  Entomologist  and  Chief  of  Bureau. 


HIBERNATION  OF  THE  MEXICAN 
COTTON  BOLL  WEEVIL. 


BY 

W.  E.  HINDS  and  AV.  W.  YOTHERS, 

UNDER  THK  DIRECTION  OF 

W.  D.  HUNTER. 


Issued  October  18,  1909. 


WASHINGTON: 

GOVERNMENT   PRINTING  OFFICE. 
1909. 


B  UREA  U  OF  ENTOMOLOGY* 

L.  O.  Howard,  En  tomologist  and  Chief  of  Bureau. 
C,  L.  Marlatt,  Entomologist  and  Acting  Chief  in  Absence  of  Chief. 
R.  S.  Cliftox,  Executive  Assistant. 
C.J.  Gilltss,  Chief  Clerk. 

F.  H.  Chittexdex,  in  charge  of  truck  crop  and  stored  product  insect  investigations. 

A.  D.  Hopktns,  in  charge  of forest  insect  investigations. 

W.  D.  Hunter,  in  charge  of  southern  field  crop  insect  investigations. 

V .  M.  Webster,  in  charge  of  cereal  and  forage  insect  investigations . 

A.  L.  Quaixtance,  in  charge  of  deciduous  fruit  insect  investigations . 

E.  F.  Phillips,  in  charge  of  bee  culture. 

D.  M.  Rogers,  in  charge  of  gipsy  moth  field  work. 

W.  F.  Fiske,  in  charge  of  gipsy  moth  laboratory. 

R.  S.  Woglum,  in  charge  of  hydrocyanic  acid  gas  investigations. 

R.  P.  Currie,  in  charge  of  editorial  work. 

Mabel  Colcord,  librarian. 

Southern  Field  Crop  Insect  Investigations. 

W.  D.  Hunter,  in  charge. 

W.  D.  Pierce,  R.  A.  Cushman,  C  E.  Hood,  E.  S.  Tucker,  engaged  in  cotton  boll 
weevil  investigations. 

F.  C.  Bishopp,  J.  D.  Mitchell,  H.  P.  Wood, ^engaged  in  cattle  tick  life  history  investi- 
gations. 

A.  C.  Morgan,  G.  A.  Runner,  engaged  in  tobacco  insect  investigations. 
D.  L.  Van  Dine,  engaged  in  sugar  cane  and  rice  insect  investigations. 
F.  C.  Pratt,  engaged  in  cactus  insect  investigations. 


"  Organization  of  the  bureau  on  September  1,  1909. 


U.  S.  DEPARTMENT  OF  AGRICULTURE, 
BUREAU  OF  ENTOMOLOGY — BULLETIN  NO.  77. 

L.  O.  HOWARD.  Entomologist  and  Chief  of  Bureau. 


HIBERNATION  OF  THE  MEXICAN 
(OTTON  BOLL  WEEVIL 


BY 

\V.  E.  HINDS  am.  W.  W.  rOTHEBS, 

UNDER  THE  DIRECTION  Of 

W.  D.  HUNTER. 


I  ssi  BD  (  >.  Tom-It  IS,  11MM). 


WASHINGTON: 

GOVERNMENT   PRINTING  OFFICE. 

1909. 


LETTER  OF  TRANSMITTAL. 


U.  S.  Department  of  Agriculture, 

Bureau  of  Entomology, 
Washington,  D.  C,  October  6,  1908. 
Sir:    I  have  the  honor  to  transmit  herewith  for  publication  as 
Bulletin  No.  77,  of  the  Bureau  of  Entomology,  a  manuscript  prepared 
by  Dr.  W.  E.  Hinds  and  Mr.  W.  W.  Yothers  under  the  direction  of 
Mr.  W.  D.  Hunter.    This  manuscript  deals  with  the  hibernation  of 
the  Mexican  cotton  boll  weevil.    The  winter  season  is  a  critical  period 
in  the  life  history  of  this  very  destructive  pest.    An  exact  knowledge 
of  its  hibernation  throws  much  light  on  practical  control.  For 
this  reason  careful  experimental  studies  have  been  carried  on  for 
several  years.    On  account  of  their  importance  the  results  are  pre- 
sented somewhat  in  detail.    The  illustrations  will  add  greatly  to  the 
clearness  and  force  of  the  text. 
Respectfully, 

L.  O.  Howard, 
En  torn  ologist  a  n  d  Oh  ief  of  Bureau. 

Hon.  James  Wilson, 

Secretary  of  Agriculture. 

2 


CONTEXTS. 


Page. 


Entrance  into  hibernation   11 

Supply  of  weevils  to  enter  hibernation   11 

Stages  entering  hibernation   L3 

Time  of  entering  hibernation   15 

Proportion  of  each  sex  among  weevils  in  fall   L6 

Number  of  adult  weevil-  entering  hibernation   17 

Temperature  conditions  producing  hibernation   20 

Shelter  during  hibernation   25 

Shelter  in  bolls   25 

Hibernation  shelter  other  than  b<.ll<  within  the  field   30 

Hibernation  shelter  outside  of  cotton  fields   31 

Hibernation  experiments  in  small  cages   33 

Cage  experiments  of  1902-8   34 

Cage  experiments  of  1903—4   34 

Cage  experiments  of  1904-5   34 

Hibernation  experiments  in  small  cages,  1!><).">  (i   35 

Large-cage  experiments,  Koatchio,  I. a..  1  !»().">  (i   3S 

Favorable  conditions  for  hibernation   11 

K fleet  of  acclimatization  upon  survival  and  emergence   42 

Relation  of  emergence  to  effective  temperatures   43 

Relation  of  time  of  entrance  into  hibernation  to  survival  and  emergence.  .  45 

The  relationship  of  accumulated  effective  temperature  to  emergence   46 

Longevity  of  weevils  after  emergence  in  Keatehie  experiment*   48 

Large-cage  experiments  Dallas,  Tex.,  1905-6  ».   49 

Nature  of  weevil  activity  following  emergence  from  hibernation   50 

Climatic  conditions  producing  emergence  from  hibernation  at  Pallas,  Tex., 

in  1906   52 

Emergence  in  the  field  at  Victoria,  Tex.,  in  1906   52 

Large-cage  experiments,  1906-7,  Dallas,  Calvert,  and  Victoria.  Tex   55 

Plan  of  experiments   55 

Climatic  conditions  producing  hibernation  and  activity  of  weevils  during 

normal  hibernation  period   57 

Entrance  into  hibernation   58 

Activity  during  normal  period  of  hibernation   G2 

Winter  activity   64 

Activity  as  shown  by  development  during  normal  hibernation  period.  ...  66 

Activity  in  the  field  during  normal  hibernation  period   67 

Emergence  from  hibernation,  1907   67 

Relationship  of  emergence  from  hibernation  to  climatic  conditions   68 

Effect  of  time  of  entering  hibernation  and  nature  of  shelter  upon  the  per- 
centage of  survival   74 

Survival  of  weevils  by  localities  and  cage  sections   77 

Monthly  summary  of  emergence  records   79 

Weekly  emergence  records   79 

3 


4 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


Tage. 


Longevity  of  weevils  after  emergence  from  hibernation   83 

Longevity  of  unfed  weevils  after  emergence  from  hibernation   84 

Longevity  of  fed  weevils  after  emergence  from  hibernation   86 

Bearing  of  observations  on  fed  and  unfed  weevils  on  the  possibility  of  avoid- 
ing damage  to  cotton  by  late  planting   89 

Sex  of  weevils  surviving  hibernation   91 

Secondary  sexual  characters   91 

Proportion  of  sexes  surviving  hibernation   92 

Relation  of  hibernated  weevils  to  food  supply   93 

Summary  and  conclusions   95 


ILLUSTRATIONS. 


PLATES. 

Pago. 

I'i.atk  I.  \V(  at  her- recording  apparatus  and  fence-row  sholtor.  Fig.  1. — 
Wfather  apparatus  used  in  recording  temperature  and  humidity 
conditions.    Fig.  2. — Typical  weedy  fence-row,  affording  excel- 


lent shelter  for  weevils   30 

II.  Favorable  shelter  conditions  in  and  around  fields.  Fig.  1. — Cotton 
field  adjoining  grove  of  trees  laden  with  Spanish  mess  i  TiUandsia 
usneoides).  Fig.  2. — Near  view  of  moss.  Fig.  3. — Cotton  stalk 
having  many  bolls  infested  by  weevils  at  hibernation  time   30 

III.  Seed  house  and  hibernation  cage,  Keatchie,  La.   Fig.  1. — Seed  house 

opposite  which  the  first  sign  of  weevil  work  was  found  at  Keatchie, 
La.,  in  1905.  Fig.  2. — Large  cage  built  for  hibernation  experi- 
ments in  1905-6   38 

IV.  Hibernation  experiments,  Dallas,  Tex.,  l9<>">-»;.    Fig.  1.  -Four-section 

•  age  used  for  experiments,  built  over  cot  ton .    Fig.  2.    Shelter  con- 
ditions as  occurring  naturally  in  section  1   50 

V.  Shelter  conditions  in  Dallas,  Tex.,  experiments.  1905-6.  Fig.  1. — 
Piled  cotton  stalks  and  piled  boxes  in  section  2.  Fig.  2. — Stand- 
ing cotton  stalks  versus  piled  leaves,  section  3   50 

VI.  Cages  for  hibernation  experiments  in  Texas,  1900-7.  Fig.  I. --Dallas, 
Tex.,  cage  on  flat,  black-waxy  land.  Fig.  2. — Calvert,  Tex.,  cage 
on  slightly  sloping,  sandy  land  in  post-oak  region.  Fig.  3. — 
Victoria,  Tex.,  cage  on  sandy-loam  slope  between  bottom  and 
upland   56 


VII.  Shelter  conditions,  Dallas,  Tex.,  cage.  Fig.  1  .—  Active  weevils  try- 
ing to  escape  through  wire  on  October  20,  1906.  Fig.  2. — Section 
I,  in  which  weevils  were  placed  October  13,  1906,  2.61  per  cent 
surviving.    Fig.  3.— Section  4,  started  October  16,  1906.4.07  per 


cent  surviving   64 

VIII.  Hanging  moss  as  affecting  hibernation  and  emergence.  Fig.  1. — 
Section  7,  with  hanging  moss  in  top  of  cage.  Fig.  2. — Same  sec- 
tion, ground  conditions,  started  October  24,  1906,  6.95  per  cent 

surviving;  emergence  ceased  June  17,  1907   74 

IX.  Shelter  conditions  producing  average  survival  at  Dallas,  Tex.  Fig. 
1. — Section  8,  started  October  30,  1906;  emergence  ceased  June  15, 
1907;  survival,  8.85  per  cent.  Fig.  2. — Section  5,  started  Novem- 
ber 5,  1906;  emergence  ceased  May  15,  1907;  survival,  12.22  per 
cent.  Fig.  3. — Section  3,  started  November  12,  1906;  emergence 
ceased  May  21,  1907;  survival,  14.74  per  cent   74 


X.  Exceptionally  favorable  conditions  and  boll  experiment.  Fig.  1. — 
Section  10,  a,  bolls  exposed  on  surface;  b,  corner  where  bolls 
were  buried  2  inches  deep,  started  December  6,  1906;  emergence 
ceased  May  2,  1907;  survival,  4.51  per  cent.  Fig.  2. — Section  9, 
stalks  left,  started  November  13,  1906;  emergence  ceased  June 
19,  1907;  survival,  25.92  per  cent   74 

5 


6 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


TEXT  FIGURES. 

Page. 


Fig.  1.  Chart  showing  mean  average  temperature,  rainfall,  and  weevil  emer- 
gence, Keatchie,  La.,  March  to  June,  1906   41 

2.  Chart  showing  mean  average  temperature,  rainfall,  and  weevil  emer- 

gence, Dallas,  Tex.,  March  to  May,  1906   53 

3.  Chart  showing  mean  average  temperature,  rainfall,  and  weevil  activity, 

Dallas,  Tex.,  October,  1906,  to  March,  1907   59 

4.  Chart  showing  mean  average  temperature,  rainfall,  and  weevil  activity, 

Calvert,  Tex.,  October,  1906,  to  March,  1907   60 

5.  Chart  showing  mean  average  temperature,  rainfall,  and  weevil  activity, 

Victoria,  Tex.,  October,  1906,  to  March,  1907   61 

6.  Chart  showing  mean  average  temperature,  rainfall,  and  emergence  from 

hibernation,  Dallas,  Tex.,  March  to  June,  1907   69 

7.  Chart  showing  mean  average  temperature,  rainfall,  and  weevil  emer- 

gence, Calvert,  Tex.,  March  to  June,  1907   70 

8.  Chart  showing  mean  average  temperature,  rainfall,  and  weevil  emer- 

gence, Victoria,  Tex.,  March  to  June,  1907   71 

9.  Secondary  sexual  characters  of  Anthonomus  grandis   91 


PREFACE. 


Natural  conditions  annually  reduce  enormously  the  numbers  of  t lie 
cotton  boll  weevil.  Although  no  two  seasons  are  exactly  alike,  never 
more  than  a  small  percentage  of  the  weevils  in  the  fields  in  the  fall  is 
permitted  to  survive  until  Bpring.  In  fact,  winter  is  the  most  critical 
season  in  the  whole  life  history  of  the  weevil.  Any  steps  in  control 
of  the  weevil  during  the  winter  are  therefore  much  more  important 
than  those  which  can  he  taken  at  any  other  season  of  the  year.  To 

desl  roy  ten  weevils  in  the  winter  is  much  better  than  to  destroy  many 
thousands  in  the  summer.  The  cotton  boll  weevil  is  now  causing  a 
damage  in  the  United  States  each  year  of  at  least  $25,000,000.  The 
indications  are  t  hat  t  hi>  amount  w  ill  cont  inue  to  be  lost  for  some  time 
at  least  on  account  of  the  difficulties  in  control  which  will  be  encoun- 
tered in  the  Mississippi  Valley.     For  these  reasons  the  Bureau  of 

Entomology  has  conducted  careful  investigations  of  the  hibernation 
of  the  weevil  and  presents  the  somewhat  detailed  results  in  this 
bullet  in. 

Until  this  time  the  hibernation  of  the  boll  weevil  has  been  less 

Undersl  I  t  han  any  other  phase  of  its  life  history.     This  was  due  to 

the  great  difficulty  in  obtaining  the  necessary  data  and  the  fact  that 
the  phenomena  of  hibernation  are  not  necessarily  identical  in  different 
seasons.  In  fact,  it  will  be  seen  from  the  following  pages  that  there 
have  been  very  important  dissimilarities  between  the  years  when 
special  observations  have  been  under  way.  The  necessary  repeated 
work  in  Large  cages  in  different  localities  has  now  been  carried  on  and 
extensive  field  observations  have  been  made  in  various  representative 
parts  of  the  infested  area  as  to  the  natural  situations  in  which  the 
hibernating  weevils  occur.  As  a  result,  tin1  present  bulletin  will 
make  the  life  history  of  the  boll  weevil  during  the  winter  season  at 
least  as  well  know  n  as  any  other  portion  of  its  biology. 

In  the  work  leading  to  this  bulletin  practical  considerations  have 
always  received  primary  attention.  However,  it  has  repeatedly  been 
shown  that  careful  detailed  investigations  of  injurious  insects  may 
result  in  important  suggestions  for  control  that  are  not  foreseen  at  the 
beginning  of  the  work.  Therefore  the  topic  of  the  hibernation  of  the 
boll  weevil  has  been  investigated  from  every  possible  standpoint. 
Its  importance,  as  a  critical  period  in  the  life  history  of  a  most  injuri- 
ous pest,  has  abundantly  warranted  this  work. 

7 


8 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


Foremost  among  the  points  of  immediate  practical  application 
shown  in  this  bulletin  is  the  enormous  importance  of  the  fall  destruc- 
tion of  the  plants.  This  has  been  one  of  the  recommendations  of  the 
Bureau  of  Entomology  for  some  years.  Its  importance  will  increase 
rather  than  diminish  in  the  regions  now  invaded  by  the  insect.  The 
cage  experiments  at  Dallas,  Calvert,  and  Victoria,  Tex.,  in  the  winter 
of  1906-7  have  given  most  important  and  accurate  data  showing 
exactly  what  may  be  accomplished  by  the  fall  destruction  of  the 
plants  at  various  dates.  This  bulletin,  moreover,  shows  the  most 
favorable  and  least  favorable  conditions  in  the  hibernation  of  the 
weevil.  This  information  can  be  put  to  practical  use  by  every  farmer 
in  the  infested  area.  It  shows  exactly  where  the  most  effective  work 
can  be  done.  A  not  unimportant  feature  is  the  showing  of  the  abso- 
lute impracticability  of  late  planting  to  obviate  damage  by  the  boll 
weevil  by  reason  of  the  remarkable  longevity  of  hibernated  individuals 
without  any  green  food  whatever. 

The  information  included  in  this  bulletin  has  been  accumulated 
through  the  investigations  and  observations  of  the  numerous  agents 
connected  with  the  work  during  the  seasons  of  1902-1907.  Some  of 
the  facts  have  been  briefly  stated  in  previous  publications,  particularly 
Bulletins  45  and  51.  The  manuscript  for  the  present  publication  was 
prepared  during  the  summer  and  fall  of  1907,  and  since  that  time 
some  of  the  conclusions  drawn  from  this  study  have  been  published  in 
connection  with  other  bulletins  and  circulars  relating  to  the  weevil 
and  its  control.  But  in  no  other  instance  have  all  of  the  facts  been 
considered  or  their  complex,  intimate,  and  important  co-relationships 
studied  as  in  this  work. 

On  account  of  the  large  amount  of  work  that  has  been  done  and  the 
practical  importance  of  many  of  the  conclusions  drawn  it  has  been 
considered  that  full  indication  should  be  made  in  the  bulletin  of  the 
methods  by  which  the  conclusions  and  recommendations  are  reached. 
Therefore  special  pains  have  been  taken  to  give  all  essential  data  and 
to  represent  by  charts  matter  that  can  thus  be  graphically  expressed. 

It  will  be  noted  that  the  various  experiments  dealt  with  in  this 
bulletin  are  taken  up  according  to  the  years  in  which  the  work  was 
carried  on.  The  result  is  that  some  special  topics,  such  as  time  of 
entrance  into  hibernation,  will  be  found  discussed  in  several  places. 
It  has  been  found  entirely  impracticable  to  follow  a  strictly  topical 
system  and  discuss  each  point  connected  with  hibernation  with  refer- 
ence to  the  work  of  the  various  years.  This  impracticability  is  due 
principally  to  the  great  natural  variations  in  the  seasons.  Never- 
theless the  first  part  of  the  bulletin  discusses  the  general  feature  of 
hibernation  and  the  summary  at  the  end  has  been  written  in  such  a 
way  ;is  to  bring  the  principal  conclusions  on  the  various  topics  into 
condensed  form. 


PREFACE. 


9 


The  question  of  credit  to  the  various  investigators  who  have  con- 
tributed to  this  bulletin  is  rather  complicated.  Mr.  E.  A.  Schwarz 
studied  carefully  the  hibernation  of  the  weevil  at  Victoria,  Tex.,  in 
the  winter  of  1901-2  and  his  observations  have  been  utilized.  Later 
Mr.  Wilmon  Newell,  secretary  of  the  State  Crop  Pest  Commission  of 
Louisiana,  assisted  by  Mr.  J.  B.  Garrett,  planned  and  executed  a 
series  of  experiments  in  the  hibernation  of  the  weevil  which  was  much 
more  extensive  than  any  similar  work  that  had  been  done  up  to  that 
time  in  this  country.  This  work  was  done  in  cooperation  with  the 
Bureau  of  Entomology,  and  the  results,  through  the  liberality  of 
Mr.  Novell,  have  been  largely  incorporated  into  this  bulletin.  Mr. 
J.  J).  Mitchell  contributed  important  facts  from  observations  during 
several  seasons,  especially  with  reference  to  actual  winter  held  con- 
ditions. Many  of  the  details  in  the  plans  for  the  extensive  work  of 
1906-7  were  worked  out  by  Dr.  \Y.  E.  Hinds,  who  also  superintended 
the  extensive  tedious  work  necessary  during  the  follow  ing  spring.  In 
all  this  work  Doctor  Binds  was  assisted  by  Mr.  \Y.  AY.  Yothers,  by 
Mr.  A.  ('.  Morgan,  who  had  charge  of  the  work  with  the  large  cage 

near  Victoria,  and  by  Mr.  ('.  K.  Jones,  who  was  located  at  Calvert. 

Mr.  Yothers  collaborated  with  Doctor  Hinds  in  the  arrangement  and 
correlation  of  the  data  obtained  at  the  places  mentioned  and  in  placing 
in  manuscript  form  the  records  of  many  of  the  experiments  of  previous 
year-.  For  two  winters  Mr.  Yothers  carried  on  special  observations, 
largely  of  his  own  planning,  as  to  actual  field  conditions.  In  this 
work  he  collected  large  quantities  of  bolls  and  various  forms  of  trash 
in  and  about  cotton  fields,  and  from  careful  examinations  of  this 
material  in  the  laboratory  he  was  able  to  determine  many  very  impor- 
tant facts  in  regard  to  the  several  classes  of  rubbish,  or  winter  shelter, 
which  are  most  likely  to  protect  weevils  and  to  insure  their  successful 

survival  through  the  winter  season. 

W.  D.  Hunter, 

///  (lianjt  of  Sout/o  rn  Ful<l  Crop 

Insect  1 1  vestigatipns. 


HIBERNATION  OF  THE  MEXICAN  COTTON  BOLL 

WEEVIL. 


ENTRANCE  INTO  HIBERNATION. 

In  the  study  of  hibernation  of  the  Mexican  cotton  boll  weevil 
(A/it/ionom us  (/ram/is  Boh.  i  we  shall  first  consider  the  factors  affect- 
ing the  abundance  of  weevils  which  may  enter  hibernation,  the 
dependence  of  the  number  of  weevils  present  upon  preceding  con- 
ditions of  food  supply,  the  climatic  conditions  accompanying  or 
producing  the  beginning  of  hibernation,  and  other  biological  facts 
which  jnay  be  of  interest  or  value  in  connection  with  this  division 
of  the  subject . 

Sl'PPLY  OF   WKKVILS  TO   EXTKI!    1 1 1  HKILN  ATION . 

The  common  name  "cotton  boll  weevil/'  which  is  uniformly 
applied  to  this  insect,  may  be  in  part  at  least  responsible  for  a  mis- 
leading impression  in  regard  to  the  most  common  point  of  attack 
and  place  of  development  of  this  weevil.  The  common  name  was 
first  applied  because  of  the  fact  that  in  the  (ir>t  recorded  case  of  this 
insect  attacking  cotton  the  specimens  were  found  in  bolls.  It  is  a 
fact,  however,  that  by  far  the  greater  number  of  weevils  to  be  found 
in  any  field  at  any  season  of  the  year  have  really  developed  within 
the  buds  or  squares  rather  than  within  the  bolls.  hi  the  first  place, 
it  is  perfectly  evident  that  during  the  entire  growing  season  of  the 
plant,  in  the  infested  area,  probably  not  much  more  than  10  percent 
of  the  squares  which  form  ultimately  produce  bolls.  For  this  reason 
the  weevils  find  opportunities  for  reproduction  many  times  greater 
in  squares  than  in  bolls.  In  the  second  place,  a  careful  study  of  the 
habits  of  the  weevils  shows  that  they  prefer  squares  both  for  feeding 
and  for  reproduction.  In  the  third  place,  the  average  period  required 
for  development  in  squares  is  only  one-half  to  one-third  as  great  as 
it  is  in  bolls  which  become  more  than  one-half  grown.  These  three 
considerations  insure  a  far  more  rapid  and  abundant  multiplication 
of  individuals  through  the  medium  of  squares  than  through  bolls. 
Wherever  weevils  have  been  present  in  average  abundance  at  the 
beginning  of  the  season,  unless  they  have  been  unusually  checked 
by  climatic  conditions  unfavorable  to  their  development .  a  condition 
of  total  infestation  of  squares  is  usually  reached  between  August  1 

11 


12  HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 

and  20.  By  this  time  practically  all  of  the  crop  which  can  be  expected 
will  have  been  set  and  many  of  the  oldest  bolls  will  be  found  maturing. 
If  a  moderate  crop  of  bolls  is  being  matured  the  formation  of  squares 
usually  ceases,  almost  if  not  entirely,  for  a  period  of  several  weeks. 
Whereas  in  the  early  part  of  the  season  female  weevils  could  find 
abundant  opportunities  for  depositing  their  eggs  in  previously  unin- 
fested  squares,  after  the  time  of  total  infestation  is  reached  such 
opportunities  practical^  cease  to  exist.  The  available  supply  of 
squares  and  bolls  becomes  too  small  to  support  the  large  number  of 
weevils  which  may  be  present,  and  conditions  become  decidedly 
unfavorable  for  their  further  multiplication.  It  is  at  this  season  of 
the  year,  usually  from  August  15  to  September  20,  that  the  largest 
general  dispersion  movements  of  the  weevils  take  place.  It  is  at  this 
season  also,  during  recent  years,  that  the  cotton  leaf-worm  has 
become  sufficiently  abundant  to  secure  a  partial  or  complete  defolia- 
tion of  the  plants.  While  the  occurrence  of  the  leaf-worms  is  by  no 
means  regular,  the  effect  of  their  work  is  to  still  further  limit  the 
available  food  supply  of  the  boll  weevil  and  to  force  them  into  a  more 
general  dispersion  from  the  defoliated  plants.  On  account  of  the 
reduced  supply  of  squares,  the  increased  period  of  development  in 
bolls,  and  the  extensive  dispersion  movements  of  the  weevil  at  this 
season  of  the  year,  it  usually  happens  that  the  actual  number  of 
individuals  in  a  field  becomes  greatly  reduced. 

Following  the  maturity  of  a  considerable  portion  of  the  crop  of 
bolls,  and  usually  in  connection  with  the  occurrence  of  a  heavy  rain- 
fall, a  renewed  growth  of  the  plant  commonly  produces  an  abundance 
of  squares.  It  is  this  late  top  growth  of  the  plant,  which  serves  no 
good  purpose  so  far  as  further  production  of  cotton  is  concerned, 
that  is  primarily  responsible  in  most  fields  for  the  needlessly  large 
number  of  weevils  produced  between  the  time  of  maturity  of  the 
crop  and  the  usual  time  of  destruction  of  the  plants  by  frost.  A 
large  proportion  of  the  weevils  which  become  adults  before  Septem- 
ber 1  may  be  expected  to  die,  either  as  cold  weather  comes  on  or 
during  the  early  part  of  the  winter  season.  The  later-developed 
weevils,  however,  have  not  exhausted  their  vitality  and  are  much 
more  likely  to  survive  the  full  hibernation  period.  The  importance, 
therefore,  of  preventing  or  of  reducing  the  formation  of  squares 
following  the  period  of  maturity  of  the  bolls  can  be  easily  appreciated. 

To  sum  up  briefly  the  principal  points  in  the  development  of 
weevils  which  may  enter  hibernation,  we  may  say  that  from  the 
beginning  of  the  formation  of  squares  until  the  plants  are  destroyed 
by  frost  the  development  of  the  boll  weevil  is  a  continuous 
process.  During  the  usual  fruiting  period  of  the  plant  it  is  possible 
thai  ;is  many  as  eight  generations  of  the  weevil  may  be  produced, 
especially  in  southern  Texas.    It  is  also  possible  that  during  (his 


ENTRANCE  INTO  HIBERNATION. 


13 


period  individuals  may  exist  which  represent  an  advance  of  only 
one  generation.  During  the  entire  season  the  average  period  required 
for  development,  in  squares,  from  the  deposition  of  the  egg  to  the 
emergence  of  the  adult  weevil  is  from  18  to  20  days.  In  bolls  the 
developmental  period  may  exceed  60  days.  The  average  period 
during  which  each  female  may  deposit  eggs  is  between  98  and  60 
days.  The  average  number  of  eggs  which  each  female  may  be 
expected  to  deposit  is  not  far  from  100.  The  average  period  required 
for  each  generation  is  between  40  and  45  days.  In  southern  Texas, 
therefore,  live  full  generations  of  the  weevil  may  usually  be  expected, 
and  owing  to  the  somewhat  shorter  season  and  lower  temperatures 
occurring  in  northern  Texas  four  generations  is  probably  the  true 
average  in  thai  section  of  the  State.  There  is  no  particular  hiber- 
nation brood,  but  representatives  of  all  generations  may  survive 
and  enter  hibernation.  From  these  considerations  it  will  be  readily 
understood  that  during  the  latter  part  of  the  season  the  multiplica- 
tion is  primarily  dependent  upon  the  fond  supply,  and  that  the  com- 
mon practice  of  allowing  stalks  to  stand  after  the  crop  becomes 
matured  is  primarily  responsible  for  a  large  proportion  of  the  weevils 
which  may  enter  hibernation. 

It  is  but  repeating  statements  which  have  been  frequently  made 

in  former  publications  of  this  investigation  to  Bay  that  the  vain 
hope  of  securing  some  top  crop  of  cotton,  in  case  there  should  be  a 
late  fall,  is  probably  the  principal  reason  which  ha^  been  urged  for 
allowing  this  growth  <>f  the  plant.  So  far  as  we  know  there  is  no 
record  of  a  top  crop  ever  having  been  secured  in  a  field  which  had 
become  thoroughly  infested  with  boll  weevils  earlier  in  the  season. 
While  it  is  true  that  in  uninfested  regions  some  top  crop  has  occa- 
sionally been  formed  and  may  occasionally  be  secured  in  the  future, 
it  is  not  putting  the  facts  too  strongly  to  say  that  within  the  weevil- 
infested  area  this  has  never  occurred  and  should  never  be  expected. 

STAGES  ENTERING  HIBERNATION. 

The  reproductive  activity  of  the  weevil  continues  steadily  until 
the  plants  are  destroyed  by  frost.  It  gradually  decreases  coinci- 
dently  with  the  gradual  decrease  in  heat.  All  stages  from  the  egg 
to  the  adult  may  be  found  in  both  squares  and  bolls,  even  after  frosts 
have  occurred.  The  immature  stages  in  squares  are  not  immediately 
killed  unless  the  freeze  is  exceptionally  severe,  but  probably  very 
few  of  these  survive  to  reach  maturity  and  to  emerge  during  the 
following  spring.  Only  those  which  are  nearly  adult  at  the  time 
frost  occurs  may  be  expected  to  emerge.  These  might  emerge  upon 
warm  days  following  the  colder  weather,  but  in  the  absence  of  a 
fresh  food  supply  would  soon  die.  In  the  fall  of  1903  Prof.  E.  D. 
vSanderson  records,  from  an  examination  of  700  squares  at  the  middle 


14 


HIBERNATION  OF  TEE  COTTON  BOLL  WEEVIL. 


of  November,  finding  79  eggs,  or  that  11  per  cent  of  the  squares 
contained  eggs.  From  an  examination  of  1,600  squares  he  states 
that  366  larvae  were  found,  showing  that  about  23  per  cent  of  the 
squares  contained  larvae  at  the  time  of  entrance  into  hibernation. 
Some  stages  may  survive  in  squares  for  a  short  time  after  the  freeze, 
but  there  are  few  records  of  weevils  entering  hibernation  at  immature 
stages  in  squares  and  surviving  to  emerge  therefrom  in  the  spring. 
These  stages  are  therefore  unimportant  from  an  economic  point  of 
view. 

With  immature  stages  entering  hibernation  in  bolls  (PL  II,  fig.  3)  the 
case  is  quite  different  from  that  in  squares.  Extensive  examinations 
have  been  made  at  various  times  in  widely  separated  localities  to  deter- 
mine the  possibility  of  these  stages  maturing  in  the  bolls  during  the 
winter  and  emerging  in  the  spring.  About  the  middle  of  November, 
in  the  winter  of  1903-4,  it  was  sufficiently  cold  at  Victoria  to  destroy 
cotton  plants.  By  the  last  week  in  December  two  hard  frosts  and 
one  freeze  had  occurred,  but  at  that  time  living  larvae,  pupae,  and 
adults  could  be  very  commonly  found  in  unopened  bolls.  Two 
weeks  later,  upon  making  another  examination,  Mr.  J.  D.  Mitchell 
found  a  smaller  proportion  of  larvae  with  more  pupae  and  adults. 
Examinations  were  also  made  on  January  17  and  31  and  February 
4  and  17,  1904.  In  the  course  of  these  examinations  23  larvae,  30 
pupae,  and  144  adults  were  found,  and  most  of  them  were  living.  At 
Terrell,  Tex.,  on  December  15,  1904,  in  examinations  of  200  bolls 
Mr.  C.  R.  Jones  found  101  larvae,  16  pupae,  and  4  adults,  all  of  which 
were  alive.  Fifteen  days  later,  in  examining  100  dry  bolls,  he  found 
20  larvae,  16  pupae,  and  8  adults.  Sixty  per  cent  of  the  larvae,  87.5 
per  cent  of  the  pupae,  and  62.5  per  cent  of  the  adults  were  alive  on 
December  30.  On  Januar}^  7,  1905,  in  an  examination  of  300  dried 
bolls  29  larvae,  19  pupae,  and  13  adults  were  found,  while  the  per- 
centage of  living,  in  each  stage,  had  fallen  to  17.2  for  larvae,  15.8  for 
pupa-,  and  7.7  for  adults.  At  Wharton,  Tex.,  after  the  middle  of 
November,  1905,  an  examination  of  52  bolls  disclosed  30  larvae  and 
2  pupae,  all  of  which  were  alive. 

These  records  might  easily  be  multiplied,  but  it  is  unnecessary 
to  do  so  to  prove  that  very  large  numbers  of  weevils  enter  upon  the 
period  of  hibernation  as  immature  stages  and  that  during  many 
seasons,  especially  in  the  southern  part  of  the  State,  a  large  per- 
cent age  of  these  complete  their  development,  and  that  many  weevils 
may  survive  until  time  for  their  emergence  in  the  spring.  This 
point  is  emphasized  especially  because  of  its  significance  in  regard 
to  the  most  advisable  method  for  destroying  the  stalks  together 
with  the  infested  unopened  bolls  which  may  remain  upon  them 
late  in  the  season.  [Jpon  page  26  will  be  found  records  showing  the 
results  of  extensive  examinations  of  bolls  during  the  winter  and 
early  spring,  w  hich  add  much  emphasis  to  this  point. 


ENTRANCE  INTO  HIBERNATION. 


15 


TIME  OF  ENTERING  HIBERNATION. 

Before  discussing  the  question  of  the  time  at  which  weevils  usually 
"enter  hibernation"  it  seems  desirable  to  explain  the  sense  in  which 
that  term  is  used.  The  action  of  t he  weevils  in  securing  shelter  from 
approaching  cold  is  not  intelligent.  It  is  probably  true  that  they 
have  no  such  sense  of  sight  as  we  commonly  understand  from  the 
use  of  that  word  and  that  their  selection  of  shelter  is  not  at  all 
guided  by  that  sense.  We  mean  by  this  that  a  weevil  on  a  cotton 
plant  can  not  see  .it  any  distance  shelter  which  might  be  attractive 
to  it  and  thereupon  fly  from  the  plant  to  the  shelter.  It  is  true  that 
cold  nights  with  a  temperature  between  40°  and  50°  F.  succeeded 
by  warm  still  days,  such  as  occur  commonly  in  the  fall,  do  seem  to 
stimulate  the  weevils  to  an  unusual  activity  both  in  flight  and  in 
crawling.  It  may  be  true  that  they  have  an  instinctive  knowledge 
of  the  approach  of  temperature  conditions  from  which  they  must 
secure  shelter,  but  it  is  also  true  that  many  weevils  remain  active 

upon  plants  lor  some  time  after  the  plants  have  been  destroyed  by 
frost  and  frequently  until  several  weeks  after  other  individuals 
have  entered  hibernation.  In  speaking  of  entering  hibernation, 
therefore,  we  mean  the  entrance  of  the  weevils  upon  a  period  of 
comparative  if  not  complete  inactivity.  Their  action  in  securing 
shelter  is  gradual  and  governed  primarily  by  the  degree  of  protec- 
tion from  the  cold  which  they  may  receive.  If  early  in  the  season 
a  weevil  accidentally  finds  shelter  which  gives  it  exceptional  pro- 
tection from  the  cold  it  will  likewise  be  exceptionally  protected  from 
heat,  and  therefore  less  likely  than  are  other  less  fortunate  indi- 
viduals to  resume  its  activity  upon  warm  days.  If  at  hist  the 
shelter  which  weexils  find  is  but  slight,  they  will  be  easily  influenced 
by  succeeding  warmth,  and  in  another  period  of  activity  will  be 
likely  to  find  better  protection.  Their  flight  upon  warm  days  un- 
doubtedly leaves  large  numbers  of  them  outside  of  the  cotton  fields, 
where  they  are  as  likely  to  find  favorable  shelter  as  within  the  fields 
themselves. 

From  this  explanation  it  will  be  understood  that  it  is  rarely  pos- 
sible to  indicate  by  a  single  date  the  time  when  weevils  enter  hiber- 
nation. It  may  be  better  expressed  as  a  period  within  the  limits 
of  which  a  large  majority,  though  possibly  not  all,  weevils  may  seek 
shelter.  Naturally  this  time  varies  according  to  the  seasonal  tem- 
perature conditions,  so  that  in  one  locality  it  may  occur  several 
weeks  earlier  in  one  season  than  in  another.  It  is  also  evident  that 
differences  in  temperature  conditions  due  to  latitude  or  altitude  will 
cause  a  similar  variation  in  the  time  when  weevils  enter  hibernation. 
In  the  following  paragraph  are  given  the  approximate  dates  which 
have  been  determined  for  this  event  at  various  localities  since  1902. 


16 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


At  Victoria,  Tex.,  large  numbers  of  weevils  were  still  active  in 
the  fields  about  the  middle  of  December,  1902,  at  which  time  direct 
observations  were  discontinued.  It  is  probable,  however,  that 
weevils  were  gradually  seeking  winter  quarters  at  any  time  after 
the  first  of  that  month.  Prof.  E.  D.  Sanderson  states  that  at  College 
Station,  Tex.,  in  1903  weevils  did  not  enter  hibernation  until  after  a 
freeze  which  occurred  on  November  18.  After  this  date  they  soon  dis- 
appeared. In  1903,  at  Victoria,  hibernation  began  between  Novem- 
ber 15  and  30.  At  several  points  between  College  Station  and  Terrell, 
Tex.,  in  1904,  hibernation  began  about  November  10  and  was  not 
complete  until  early  in  December.  During  this  same  year  at  Victoria 
it  occurred  during  the  period  from  November  11  to  about  December 
8.  The  following  year  at  Victoria  it  did  not  occur  until  after  Decem- 
ber 15,  while  in  1906  at  the  same  place  weevils  entered  hibernation 
between  November  9  and  20.  At  Dallas,  Tex.,  in  1905,  few  weevils 
entered  hibernation  before  the  end  of  November,  when  heavy  frosts 
occurred,  but  they  disappeared  in  the  fields  during  the  first  few  days 
of  December.  At  Dallas  in  1906  weevils  entered  hibernation  between 
November  15  and  December  1. 

These  conclusions  as  to  the  approximate  periods  when  weevils 
entered  hibernation  are  based  upon  field  observations  which  showed 
the  gradual  disappearance  of  the  weevils  from  the  plants.  The  con- 
clusions from  field  observations  are  supported,  also,  by  those  from 
cage  experiments. 

PROPORTION  OF  EACH  SEX  AMONG  WEEVILS  IN  FALL. 

Determinations  of  sex  proportion  among  weevils  in  midsummer 
have  shown  that  during  that  period  the  sexes  exist  in  approximately 
equal  numbers.  As  the  development  becomes  retarded  by  approach- 
ing cold  weather  there  seems  to  be*  a  tendency  toward  the  production 
of  more  males  than  females.  The  generally  longer  life  of  males  may 
also  account  in  part  for  the  increased  proportion  of  that  sex,  which 
is  shown  in  the  following  table : 

Table  I. — Proportion  of  male  and  female  weevils  at  time  of  entering  hibernation. 


Year. 

Male. 

Female. 

Number. 

Per  cent. 

Number. 

Per  cent. 

1904  

557 

03.7 

317 

36.3 

1905  

03 

57.7 

127 

42.3 

1900  

173 

78 

1906  

173 

127 

190(1  

19 

57.0 

14 

42.  4 

1904  

31 

02.0 

19 

38.0 

1900  

2!) 

52.  7 

2<i 

47.  3 

1,0  ir> 

00.0 

708 

40.0 

ENTRANCE  INTO  HIBERNATION. 


17 


From  this  record  it  appears  that  at  the  time  of  entering  hiberna- 
tion male  weevils  largely  predominate,  being  in  the  proportion 
approximately  of  3  males  to  2  females. 

NUMBER  OF  ADULT  WEEVILS  ENTERING  HIBERNATION. 

It  is  evident  that  determinations  bearing  upon  the  number  of 
adult  weevils  entering  hibernation  must  in  all  cases  be  Largely  in 
the  form  of  estimates  because  of  the  physical  impossibility  of  making 
a  thorough  examination  of  more  than  a  comparatively  small  fraction 
of  an  acre.  In  our  own  determinations  upon  this  point  we  have  fol- 
lowed the  genera]  plan  of  selecting  average  crops  of  plants  in  four 
or  five  different  portions  of  the  held,  representing,  so  far  as  may  be 
possible,  different  conditions  in  the  growth  of  the  plants  which  may 
influence  the  number  of  weevils  to  be  found.  The  number  of  plants 
per  acre  IS  ultimately  the  basis  upon  which  the  estimate  as  to  the 
number  of  weevils  per  acre  is  based.  It  is  evident  that  the  number 
of  plants  will  vary  widely  in  different  localities.  For  example,  in 
the  river  valleys,  where  the  growth  of  the  plants  is  rank,  the  average 
number  may  be  about  0,000;  w  hereas  upon  poorer  land,  where  plants 
never  become  large,  the  number  per  acre  may  be  as  great  as  10,000. 
From  estimates  made  upon  several  hundred  fields  during  the  past 
two  years  it  appears  that  the  average  number  of  plants  pel'  acre  is 
not  far  from  7,ooo.  We  believe  that  this  method  of  estimating 
the  number  of  weevils  per  acre  is  more  desirable  and  reliable  than  an 

estimation  of  the  number  of  weevils  per  plant  in  which  the  fractions 
found  in  an  average  must  be  disregarded. 

In  the  fall  of  1WKJ  Prof.  K.  I).  Sanderson  found  from  his  own  obser- 
vations and  from  reports  of  correspondents  an  average  of  from  one 
to  two  weevils  per  plant.  In  the  fall  of  11)0  1  an  examination  of 
four  fields  at  Terrell,  Tex.,  showed  a  variation  of  between  7(Y2  ami 
over  29,000  weevils  per  acre.  Hus  wide  variation  was  due  primarily 
to  the  effect  of  defoliation  by  the  cotton  leaf-caterpillar  in  one  field, 
that  having  t  he  except  ion  ally  large  number  of  weevils  not  having  been 
defoliated.  These  points  are  mentioned  particularly  to  show  the 
wide  variation  which  may  occur  within  very  short  distances  and  also 
to  emphasize  the  effect  of  the  work  of  the  leaf-worm  in  accomplish- 
ing what  is  practically  a  more  or  less  complete  destruction  of  the 
stalks. 

9031 7- Bull.  77—09  2 


18 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


Table  II. — Counts  to  determine  number  of  weevils  per  acre  at  time  of  entrance  into 
hibernation,  in  three  localities  in  Texas. 


Locality. 


Plants 
per  acre. 


Plants 
exam- 
ined. 


Weevils 
found. 


"Weevils 
per  acre. 


Remarks. 


Terrell . . 

 do... 

 do... 

 do... 


Averages  and  totals. 


Calvert. 
 do.. 

....do.. 

 do. 

 do. 

 do. 

 do. 


Averages  and  totals. 


Wharton. 
....do... 
....do... 
....do... 
....do... 
....do... 


Averages  and  totals. 


10,890 
10,890 
10,890 
10,890 


10,890 


6,200 
6,200 
6,080 
6,200 
6,200 
7,000 


6,313 


100 
100 
70 
50 


320 


139 


340 


204 


29,076 
6,643 
762 
1,742 


11,570 


7,260 

30 

4 

968 

7,260 

40 

79 

14,338 

7,260 

30 

4 

968 

7,260 

30 

9 

2,178 

7,260 

30 

39 

9,438 

7,260 

30 

4 

900 

7,260 

50 

21 

3,049 

7,260 

240 

160 

4,840 

6,355 
2,073 
58,368 
2S.520 
1,000 
50,000 


,266 


Not  defoliated  by  leaf-worm . 
Defoliated. 

Do. 

Do. 

Average  four  fields  examined 
at  Terrell. 

Defoliated. 
Do. 

Not  defoliated. 
Defoliated. 
Defoliated  once. 

Do. 
Defoliated. 

Average  seven  fields  exam- 
ined at  Calvert. 


Not  defoliated. 
Do. 

Manv  squares. 
Do. 

Grazed  by  cattle. 
Estimate  reduced. 

Average  six  fields  examined 
at  Wharton. 


In  connection  with  the  work  done  at  Dallas  during  the  fall  of  1906 
repeated  estimates  of  the  number  of  weevils  per  acre  to  be  found 
upon  the  stalks  were  made  in  the  same  field  beginning  October  12, 
1906,  and  ending  January  21,  1907.  These  figures  are  presented  in 
Table  III.    The  number  of  plants  per  acre  in  this  field  was  8,300. 

Table  III. — Number  of  weevils  per  acre  upon  stalks  at  different  dates  at  Dallas,  Tex. 


Plants 

Living 

Living 

Date. 

exam- 

weevils 

weevils 

ined. 

found. 

per  acre. 

1906. 

Oct.  12  

110 

122 

9,205 

Oct.  31  to  Nov.  3 

84 

190 

18,774 

Nov.  10  

60 

106 

14,663 

Nov.  20  

35 

29 

6,877 

Nov.  22  

35 

27 

6,403 

Dec.  1  

36 

10 

2,306 

Dec.  18  

35 

5 

1,186 

1907. 

Jan.  21  

35 

3 

711 

The  table  given  above  shows  a  number  of  points  which  are  of 
exceptional  interest.  About  November  1  it  may  be  seen  that  the 
number  of  weevils  present  was  more  than  double  the  number  of  plants. 
After  that  time  there  was  found  to  be  a  steady  decrease  in  the  number 
of  weevils  present  upon  the  stalks.  The  most  abrupt  change  w  as 
to  be  found  between  November  10  and  20,  when  more  than  one-half 


ENTRANCE  INTO  HIBERNATION. 


19 


of  the  weevils  seem  to  have  left  the  plants.  This  decrease  may  be 
attributed  to  several  factors.  First,  the  weevils  were  gradually 
leaving  the  plants  through  flight,  which  may  have  carried  them  out- 
side the  fields,  and,  second,  many  were  seeking  and  remaining  in 
shelter  which  was  to  be  found  upon  the  ground  within  the  field.  A 
hard  freeze  preceded  by  low  temperatures  during  several  days  occurred 
on  November  19.  However,  the  examinations  made  on  November 
20  and  22  showed  many  weevils  present  in  the  frozen  squares  and 
especially  upon  the  bolls.  It  is  apparent  that  these  weevils  did  not 
immediately  leave  the  plants,  but  remained  upon  the  bolls  and 
squares  as  long  as  the  latter  might  serve  as  a  food  supply.  But 
within  a  few  days  all  squares  and  foliage  became  perfectly  dry,  and 
after  this  especially  weevils  became  less  active.  The  numbers  which 
were  found  upon  the  plants  after  December  1  may  be  considered  in 
a  rather  strict  sense  as  in  hibernation.  The  shelter  which  they  could 
obtain  was  comparatively  slight,  and  in  the  last  examination,  made 
on  January  21,  about  25  per  cent  of  the  weevils  found  upon  the  bolls 
still  hanging  to  the  stalks  were  dead. 

I  n  reference  to  Table  II  attention  may  be  called  to  the  exceptionally 
large  number  of  weevils  found  at  Wharton  in  one  field  on  November 
14.  This  was  a  field  of  about  5  acres  in  extent,  and  at  the  time  it 
was  examined  the  plants  were  exceptionally  large  and  ven  luxuriant 
in  growth,  showing  an  abundance  of  squares.  Very  few  bolls  had 
been  set,  so  that  the  entire  growth  of  the  plants  seems  to  have  been 
turned  to  the  production  of  squares.  As  has  been  shown  in  pre- 
ceding paragraphs,  such  conditions  would  favor  directly  the  produc- 
tion of  an  abnormally  large  number  of  weevils  per  acre.  The  fact 
that  more  than  6,000  weevils  were  actually  collected  in  this  field 
makes  it  even  more  certain  that  the  estimate  given,  while  possibly 
high,  is  not  impossible.  It  may  be  considered  as  representing  fully 
the  maximum  number  of  weevils  which  it  is  possible  for  an  acre  of 
cotton  to  support  even  under  conditions  which  are  most  favorable 
to  their  development.  Another  series  of  examinations  made  before 
and  after  the  freeze  referred  to  at  Dallas  in  a  preceding  paragraph 
should  be  considered  in  connection  with  'Fable  III  as  serving  to  show 
the  correlation  between  the  disappearance  of  the  weevils  from 
t  he  plants  and  t  heir  occurrence  under  shelter  on  the  ground  during  t  he 
period  when  they  are  entering  hibernation. 


20  HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


Table  iV. — Number  of  weevils  under  rubbish  on  ground  at  Dallas,  Tex. 


Field. 

Date  ex- 
amined. 

Portion 
of  acre 
examined. 

Wot 

w  et 
four 

Alive. 

vils 
id — 

Dead. 

Total 
per  acre. 

Percent- 
age 
alive. 

Remarks. 

1906. 

A  

Nov.  15 

22  plants. 

,  4 

0 

1,450 

100.0 

In  cracks  of  ground  around  bases 

of  plants. 

A  .'. 

...do  

1/264 

4 

0 

1,056 

100.0 

Under  rubbish  on  ground. 

A  

Nov.  22 

1/347 

8 

0 

2,776 

100.0 

Do. 

A  

Dec.  18 

1/264 

5 

14 

5,016 

26.3 

Do. 

1907. 

B  

Jan.  11 

10/8384 

5 

2 

5,870 

71.4 

Northeast  corner  of  field. 

C   

Jan.  29 

10/6236 

1 

1 

1,247 

50.0 

Middle  of  field. 

C  

...do  

10/8384 

2 

2 

3,354 

50.0 

Near  southwestern  edge. 

The  sum  total  of  weevils  found  both  on  plants  and  on  the  ground 
on  November  22  shows  an  average  of  slightly  more  than  9,000  weevils 
per  acre,  all  of  which  were  alive.  On  December  18  the  number  that 
could  be  accounted  for  was  between  6,000  and  7,000  per  acre  on  the 
same  ground  which  had  been  previously  examined.  On  the  former 
date  more  than  two-thirds  of  the  weevils  were  still  upon  the  plants. 
On  the  latter  date  nearly  five-sixths  of  them  were  on  the  ground  and 
among  those  on  the  ground  but  26  per  cent  were  living.  These  fig- 
ures show  that  between  November  22  and  December  18  a  very  large 
mortality  had  occurred  among  weevils  which  had  entered  hiberna- 
tion and  especially  among  those  which  had  sought  shelter  under  rub- 
bish upon  the  surface  of  the  black-waxy  soil  of  field  A. 

There  is  some  evidence  indicating  that  there  is  normally  a  greater 
mortality  among  the  weevils  hibernating  at  the  surface  of  heavy 
black  soil  than  that  occurring  among  weevils  which  hibernate  on  the 
surface  of  sandy  soil.  The  reason  for  whatever  difference  there  may 
really  be  in  this  mortality  would  seem  to  be  quite  directly  attributa- 
ble to  the  difference  in  drainage  conditions  in  the  two  types  of  soil, 
and  to  the  characteristic  adhesiveness  of  the  black  type.  It  is  quite 
likely  that  the  difference  is  sufficient  to  justify  different  methods  of 
treatment  for  the  two  classes,  but  our  knowledge  of  the  constant 
variations  and  the  effective  factors  is  not  yet  sufficiently  complete  to 
justify  us  in  making  specific  recommendations. 

TEMPERATURE  CONDITIONS  PRODUCING  HIBERNATION. 

It  is  evident  that  the  exact  time  at  which  weevils  begin  to  enter 
hibernation,  and  that  at  which  the  entrance  into  hibernation  be- 
comes complete,  can  be  determined  only  approximately.  The  evi- 
dence consists  largely  of  observations  showing  the  decrease  in  the 
number  of  weevils  which  are  active,  the  finding  of  weevils  in  a  quiet 
condition  within  various  classes  of  shelter,  the  changes  in  activity  of 
weevils  confined  in  cages,  the  cessation  of  feeding  and  of  reproductive 


ENTRANCE  INTO  HIBERNATION. 


21 


activity,  and  the  general  relationship  of  temperature  to  conditions  of 
food  supply  and  weevil  activity.  In  the  following  tables  are  shown 
the  maximum  and  minimum  temperature  occurring  throughout  the 
period,  which  has  been  approximately  determined  for  each  of  the 
localities  indicated  in  the  respective  seasons.  The  maximum  tem- 
perature is  given  above  and  the  minimum  temperature  below  the  line 
for  each  day.  Wherever  the  climatic  record's  for  a  particular  locality 
are  incomplete  it  has  been  necessary  to  use  those  forsonie  <  >t  her  near-by 
locality.  The  table  shows  at  a  glance  the  daily  range4  of  temperature 
in  each  case,  which  undoubtedly  has  considerably  more  significance4 
in  regard  to  the  entrance  of  weevils  into  hibernation  than  would  the 
figures  showing  simply  the  mean  daily  temperature.  The  table  as 
arranged  shows  a  comparison  of  the  records  of  all  localities  during 
each  season  successively. 


22 


HIBEKNATION  OF  THE  COTTON  BOLL  WEEVIL. 


S3  2 


lO      1(31  w      O  I  CO  0)10 


3  g 


5S  S 


5  So 


3  g 


od 

00 

oo 

od 

g 
0 

8 
Pi 

s 

§ 
P 

ft 

* 

> 

o 

> 
o 

o 

o 

o 

ft 

3  i 


ENTRANCE  INTO  HIBERNATION. 


I-  N 

s|s 

s; 

-r 

-r 

n 

*|S 

S  |     !       :  :S 

1  a  1  !    i    ;  ■! 

a 

1  *  \ 

3  3 

s|s 

2  1 

s|s 

n 

X 

T 

"  sis 

00 

-  ^ 

s|s 

5  3 

5  5 

t» 

s|& 

s|s 

IB 

s|s 

-  y 

«o 

5 

s|a 

S|2 

S3  3 

-r 

s|9 

Jo  |  s 

S|fo 

Se  2 

M 

s|s 

3  9 

s|& 

s|s 

!:  3 

8  S 

C-« 

e|s 

S3 

e|s 

Eg  3 

11 

24  HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 

This  table  serves  to  show  in  a  graphic  way  the  extent  of  the  period 
of  entrance  into  hibernation,  the  varying  duration  of  the  period 
for  the  same  locality  in  different  seasons,  and  the  generally  later 
date  of  entrance  in  southern  localities  as  compared  with  more  northern 
localities  in  the  same  season.  It  also  shows  the  duration  of  the 
period  as  compared  with  the  mean  average  temperature  prevailing. 
In  general  it  appears  that  the  greater  the  drop  in  temperature  the 
shorter  will  be  the  period  of  entrance  into  hibernation. 


Table  VI. — Periods  of  entrance  into  hibernation,  and  temperatures. 


Year. 

Locality. 

Period. 

Temperature. 

Limits. 

Days. 

Mean 
average. 

Effective.^ 

1903.... 

College  Station,  Tex  

Nov.  15-27  

13 

49.5 

6.5 

1903.... 

Victoria,  Tex  

Nov.  15-30  

16 

53.0 

10.0 

1904.... 

Corsicana,  Tex  

Nov.  10-Dec.  5. . 

26 

55.0 

12.0 

1904.... 

Victoria,  Tex  

Nov.  11-Dec.  8. . 

28 

57.5 

14.5 

1905.... 

Dallas,  Tex  

Nov.  29-Dec.  8.. 

10 

40.5 

None. 

1905.... 

Victoria,  Tex  

Nov.  30-Dec.  18. 

19 

50.0 

7.0 

1900.... 

Dallas,  Tex  

Nov.  12-Dec.  8. . 

27 

53.0 

10.0 

1906.... 

Victoria,  Tex  

Nov.  9-Dec.  21.. 

43 

60.4 

17.4 

a  In  studying  the  relationship  of  temperature  conditions  to  weevil  activity  the  term  "effective  tem- 
perature" is  used  to  designate  the  excess  of  temperature  above  43  degrees  F.  It  has  been  estimated  that 
43  degrees  marks  approximately  the  beginning  of  activity  with  most  animals,  and  experiments  have  shown 
that  this  is  equally  true  of  the  boll  weevil.  Below  this  temperature  the  weevils  are  usually  inactive. 
Above  it  they  may  move,  feed,  and  reproduce  with  increasing  rapidity  as  the  temperature  increases.  From 
this  explanation  it  may  be  readily  undei stood  that  the  column  showing  the  decrease  of  effective  tem- 
perature is  really  the  most  significant  in  connection  with  the  inactivity  or  hibernation  of  the  weevil. 

It  is  undoubtedly  true  that  minimum  temperatures  have  a  special 
influence  in  checking  the  activity  of  the  weevil  in  spite  of  the  fact 
that  they  may  be  below  43  degrees  F.  When  the  temperature  falls 
to  32  degrees  or  lower  the  food  supply  of  the  weevils  is  usually  rather 
completely  destroyed,  and  this  fact  may  serve  to  discourage  subsequent 
activity  on  the  part  of  the  weevils,  even  though  the  temperature 
conditions  might  otherwise  favor  it. 

From  this  table  it  may  be  seen  that  the  shortest  period  of  entrance 
into  hibernation  of  which  we  have  record  is  ten  days.  This  occurred 
at  Dallas,  when  the  mean  average  temperature  was  9  degrees  lower 
than  that  for  any  other  period  which  has  been  studied. 

In  regard  to  the  limits  assigned  to  the  period  for  Victoria  in  1906 
it  may  be  stated  that  hibernation  was  probably  only  partial  at  that 
place  at  any  time  during  the  winter  of  1906-7.  The  limits  of  the 
period  that  have  been  given  are  based  on  field  notes  made  about  the 
middle  of  November  indicating  the  beginning  of  the  period,  and 
temperature  records  covering  the  coldest  period  that  occurred  during 
December.  The  mean  average  temperature  during  November  for  Vic- 
toria was  60.4  degrees,  the  range  being  from  an  absolute  minimum  of 
27  degrees  to  an  absolute  maximum  of  84  degrees.    The  temperature 


SHELTER  DURING  HIBERNATION. 


25 


fell  below  32  degrees  only  once  during  this  month.  From  December 
1  to  21  the  mean  average  temperature  was  also  00.4  degrees.  In 
this  case  the  range  of  temperature  varies  from  an  absolute  maximum 
of  83  degrees  to  an  absolute  minimum  of  32  degrees,  the  latter  occur- 
ring only  once.  From  these  records  it  is  apparent  that  the  climatic 
conditions  were  not  sufficiently  severe  either  to  destroy  absolutely 
the  food  supply  of  the  weevils  or  to  insure  the  continued  inactivity 
of  those  which  may  have  sought  shelter  during  the  short  periods  of 
cool  weather.  Sprout  cotton  was  exceptionally  abundant  throughout 
the  winter  and  weevils  were  found  feeding  upon  it  almost  continuously. 

From  these  facts  we  may  be  justified  in  concluding  that  a  mean 
average  temperature  of  GO  degrees  is  too  high  for  the  complete  hiberna- 
tion of  the  weevil:  that  hibernation  usually  takes  place  coincidently 
with  the  decrease  in  mean  average  temperature  to  about  55  degrees ; 
and  that  it  remains  complete  until  the  mean  average  temperature 
subsequently  rises  to  above  60  degrees. 

SHELTER  DURING  HIBERNATION. 

While  many  weevils  seek  hibernal  ion  shelter  outside  the  field  it 
is  certain  that  a  considerable  number  of  them  remain  very  near  their 

food  supply  that  is,  in  the  cotton  fields  and  in  the  immediate 
vicinity.  Because  of  the  differences  in  the  nat  ure  of  t  he  weevil  shelter 
and  in  the  possibility  of  destroying  or  rem< >\ ■  i i i ir  such  favorable 
shelter,  within  and  without  the  cotton  fields,  these  two  conditions 
will  be  considered  separately. 

BHELTEB  l\  BOLLS. 

Within  the  cotton  fields  weevils  are  sheltered  primarily  in  the 
hanging  cotton  bolls,  the  fallen  foliage,  and  grass  OT  other  rubbish 
which  may  have  accumulated  upon  the  surface  of  the  ground. 
Attention  has  already  been  called  to  the  fact  that  many  stages  enter 
the  period  of  hibernation  in  an  immature  condition  in  unopened 
bolls.  (vSee  p.  14.)  That  many  adult  weevils  hibernate  entirely 
within  the  protection  afforded  by  the  bracts  and  hulls  of  bolls  has 
been  abundantly  demonstrated  (PI.  II,  fig.  3).  Rather  extensive 
experiments  have  been  made  upon  this  point  in  a  number  of  localities 
during  several  seasons.  The  principal  data  resulting  from  these 
investigations  are  presented  in  the  following  two  tables.  Table  VII 
si  lows  a  comparison  of  the  records  for  several  localities  during  four 
months  of  the  winter  of  1904-5.  During  this  period  the  prevailing 
climatic  conditions  were  the  most  severe  that  the  weevil  has  en- 
countered since  invading  Texas.  The  table  shows  therefore  a 
gradual  decrease  in  the  number  of  living  stages  present  as  the  season 
advanced. 


26 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


Table  VII. — Decrease  in  percentage  of  stages  surviving  in  bolls  from  December,  1904, 

to  March,  1905. 


December. 

January. 

Stages  alive. 

>rms. 

Stages  alive. 

>rms. 

Locality. 

Adults. 

d 

to 
a 

Adults. 

d 

M 

a 

)lls  examined. 

> 

ft 

)t  emerged .« 

Emerged,  a 

)lls  having  liv 

>rms  found  liv 

)lls  examined. 

u 

& 
ft 

e 

i 

s 

1 

o 

E  merged  .a 

)lls  having  liv: 

irms  found  liv 

pq 

03 

0 
ft 

pq 

03 

d 
P4 

n 

Terrell,  Tex 
Keatchie,  La. 

300 

113 

30 

9 

0 

P.  ct. 
48 

P.  ct. 

92 

3, 678 
1,120 

38 
3 

16 
0 

3 
2 

6 
3 

Per  c«. 
1.98 
.70 

Per 

7.3 
26.0 

Dallas,  Tex  

Calvert,  Tex  

Palestine,  Tex 

150 

10 

1 

0 

0 

7 

91 

2, 100 

0 

1 

1 

10 

.50 

10.0 

Victoria,  Tex  

3,257 

11 

7 

9 

18 

1.37 

61.0 



Totals  and 
averages. . 

450 

123 

31 

9 

0 

36 

91 

10, 155 

52 

24 

15 

37 

1.15 

11.8 

Locality. 


Terrell,  Tex  

Keatchie,  La  

Dallas,  Tex  

Calvert,  Tex  

Palestine,  Tex. . 
Victoria,  Tex... 

Totals  and 
averages. . 


February. 


1,500 
1,450 


2  .  746 


6,  496 


Stages  alive. 


Adults. 


Per  ct. 
0. 26 
.34 


.29 


Per  ct. 
1.5 
15 


8.6 


4.  1 


March. 


208 
100 
2,176 
1,599 
1,438 


Stages  alive. 


Adults. 


Per  ct. 


Per  ct. 


a  In  Tables  VII  and  IX  the  designation  "not  emerged"  is  used  for  those  stages  and  adults  which  have 
not  left  the  cells  in  which  they  developed.  Adults  which  have  previously  left  the  cells  within  which 
they  matured  and  have  subsequently  sought  shelter  within  any  part  of  the  bolls  are  designated  as 
"emerged." 

Besides  showing  that  large  numbers  of  weevils  entered  hibernation 
in  or  upon  these  bolls,  this  table  shows  that  bolls  do  not  provide 
sufficient  shelter  to  insure  the  survival  of  hibernating  weevils  in  a 
winter  so  severe  as  was  that  of  1904-5. 


SHELTER  DURING  HIBERNATION. 


27 


Table  VIII.  -Climatic  conditions  ai  Dallas,  Calvert,  Palestine,  and  Victoria,  Tex., 
ami  at  Keatchie,  La.,  December  1.  V.H).',,  to  March  SI,  IfHJ'j,  producing  compile  mor- 
tality of  weevils  hibernating  in  bolls. 

DECEMBER.  1904. 


Temperature. 

Rainfall. 

Locality. 

Times 
below 

32°  F. 

Absolute 
mini- 
mum. 

Average 
mini- 
mum. 

Monthly 
mean. 

Depar- 
ture from 
normal. 

Depth. 

Depar- 
ture from 
normal. 

Dallas.  Tex  

15 

6 

•jr. 

20 

•jr. 

33.1 

•jr. 

46.6 

°F. 
-  1.2 

Inches. 
0. 74 

• 

Indus. 
-1.40 

22 

39.4 

IN.  11 

-  .5 

9.  62 

-1-4.94 

Calvert,  Tex.t  

Palestine,  Tex  

14 

5 

21 

22 

37.0 
40.  1 

50.0 
19.  ii 

-1-  .1 
-  1.8 

2.  5N 
4.08 

-  .04 
+  .27 

Victoria,  Tex  

5 

30 

44.1 

54.8 

-  3.0 

1.59 

-  .26 

Average  

9 

38.8   |  50.0 

-  1.3 

3.  70 

+  .702 

JANTAKY.  190.-,. 


24 

12 

27.8 

38.7 

-  6.2 

3.05 

4-0.33 

12 

17 

33. 6 

41.0 

-  4.9 

4.13 

-  .47 

Calvert.  Tex.  '<  

13 

16 

34.1 

ll.s 

-  3.1 

2. 01 

-  .44 

11 

18 

34.7 

43.0 

-  2.8 

2.  <H. 

-2.25 

Victoria,  Tex  

6 

25 

43.1 

53.0 

-  .6 

3.  M 

+  1.41 

Average  

13 

34.66 

44.1 

-  3.52 

3.02 

-  .284 

KEHRI' AKY,  190.",. 


Dallas.  Tex  

n 

2 

24.6 

35.2 

-  9.4 

2.81 

+  1.11 

Keatchie,  La. "  

19 

6 

31.4 

39.4 

-11.8 

1.  12 

-  .04 

Calvert,  Tex.  

21 

10 

2S. 

39.2 

-10.7 

3. 02 

+  1.20 

Palestine,  Tex  

21 

6 

31.9 

40.0 

-11.0 

2.47 

-1.00 

Victoria,  Tex  

10 

20 

34.7 

4a,  l 

-  9.9 

8.63 

+  1.42 

Average  

20 

8.8 

30.2 

39.  6 

-10.6 

3.21 

+  .59 

MARCH,  1905. 


Dallas,  Tex  

0 

35 

17.  1 

59.6 

+ 

4.0 

4.44 

+  1.29 

Keatchie.  La.'-  

0 

42 

.53.5 

02.6 

5.0 

5. 03 

+  .39 

Calvert.  Tex.b  

0 

35 

51. 6 

62.1 

i 

4.4 

4.95 

+  2. 34 

Palestine.  Tex  

0 

37 

53.7 

62.  4 

+ 

2.5 

3.  95 

+  .14 

Victoria,  Tex  

0 

46 

57.2 

05.8 

+ 

3.1 

5.04 

+  3.  52 

Averaee.  

0 

52.6 

6Z5 

+ 

3.8 

4. 68 

+  1.54 



n  Temperatures  for  Shreveport,  La.  >•  Temperatures  for  Hcarne,  Tex. 


An  examination  of  this  table  shows  that  the  temperature  went  below 
freezing  with  remarkable  Frequency  during  this  period.  The  most 
severe  cold  weather  occurred  during  February,  when  the  temperature 
averaged  10  degrees  or  more  below  normal  throughout  the  State  of 
Texas.  The  absolute  minimum  for  this  season  at  the  five  points 
mentioned  is  recorded  by  the  Weather  Bureau  as  being  2  degrees 
above  zero  at  Dallas.  At  Calvert  the  minimum  temperature  was  10 
degrees  and  at  Victoria  20  degrees.  In  most  of  the  localities  there 
was  an  excess  of  rainfall,  so  that  the  winter  as  a  whole  may  be 
characterized  as  having  been  unusually  cold  and  wet. 


28 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


While  these  records  show  that  few  if  any  weevils  survived  in  the 
shelter  of  bolls  during  tins  season  it  must  be  remembered  that  the 
weevils  were  not  exterminated  in  all  of  these  localities.  Other  con- 
ditions of  shelter  were  evidently  so  much  more  favorable  than  bolls 
as  to  have  enabled  the  weevils  to  survive  tins  severe  winter.  It  is 
true,  however,  that  in  the  spring  of  1905  weevils  occurred  in  much 
smaller  numbers  than  is  usually  the  case. 

Other  examinations  of  bolls  show  that  in  the  northern  portion  of 
the  infested  area  of  Texas  there  is  a  smaller  percentage  of  living  stages 
in  the  bolls  than  in  the  southern  portion.  The  data  for  three  seasons 
are  compared  in  Table  IX.  The  periods  selected  are  during  the 
last  of  the  winter  season  in  each  year. 

Table  IX. — Increase  in  percentage  of  survival  in  bolls  from  northern  to  southern  Texas. 


Section. 


March,  1904. 


Bolls 
exam- 
ined. 


Stages  alive. 


Adults. 

■6 

•d 
o 

£? 

if 

© 
- 

1 

0 

0 

0 

23 

28 

Bolls 

having 
living 
forms. 


Living 
forms. 


February  and  March,  1905. 


Stages  alive. 


Bolls 
exam- 
ined. 


Adults. 


Bolls 

having 
living 
forms. 


Living 
forms. 


Northern  

Central  

Southern  

Brownsville. 


2,000 
180 
250 


Per  ct. 
0 

0. 55 


Per  ct. 
0 


3,258  4 

4.575  0 

9,589  j  4 

809  0 


1 

0  0 

1  4 
0  4 


Per  ct. 

0.27 
.00 
.24 

1.80 


Per  ct. 
0.026 
.000 


February  and  March,  1906. 

Total. 

Stages  alive. 

Section. 

Bolls 
exam- 

Adults. 

Bolls 
having 
living 
forms. 

Living 
forms. 

Bolls 
exam- 

Stages 
found 

ined. 

> 

e 
£ 

Not 
emerged. 

Emerged. 

ined. 

alive. 

Northern  

6, 186 

0 

0 

1 

5 

2 

Per  ct. 
0. 04 

Per  ct. 
0 

12,044 
11,405 

12 

Central  

6,650 

0 

0 

11 

.24 

0 

17 

Southern  

1,410 

0 

0 

1 

10 

.78 

0 

11,249 
809 

85 

Brownsville   

15 

It  is  noticeable  that  there  is  a  gradual  increase  in  the  living  stages 
from  north  to  south,  and  that  toward  the  end  of  the  hibernation  period 
nearly  all  of  the  living  stages  are  adults,  most  of  which  had  matured 
before  the  beginning  of  hibernation. 

That  the  increased  mortality  found  in  bolls  during  the  winter  of 
L904  5  can  not  be  attributed  entirely  to  the  exceptional  severity  of 
that  season  is  shown  by  the  fact  that  a  similar  decrease  in  the  per- 


SHELTER  DURING   1 1 1 15  KR  NATION. 


29 


cent  age  of  living  stages  was  found  in  examinations  during  January 
and  February  of  1906.  In  January  among  1,933  bolls  examined  in 
several  localities  86  adults  and  stages  were  found.  In  February 
14,246  bolls  were  examined  and  only  30  adults  were  found.  The 
lowest  temperature  experienced  during  January  was  12°  F.  at  Dallas, 
with  the  mean  temperature  of  49.6°  F.  in  an  average  of  the  eight  locali- 
ties where  the  examinations  were  made.  During  February  the  abso- 
lute minimum  was  15°  F.  at  Dallas  and  the  average  minimum  38.5°  F. 
During  these  two  months  in  the  localities  where  examinations  were 
made  the  minimum  temperature  went  below  :V2  degrees  on  an  aver- 
age of  only  nineteen  days. 

Tablk  X.  —  <  'limutir  conditions  at  ( it/fit  /mints  in  Ttras,  January  to  March,  1906. 

JAXl'AKY. 


TcmjxTatinv. 

I'M  rip 

tation. 

Local  it  y. 

Times 

Ih-Iow 
;s_-  F. 

Ahsolute 

mini- 
mum. 

A  veragc 
mini- 
mum. 

Monthly 
mean. 

Depar- 
ture from 
normal. 

Depth. 

Depar- 
ture from 
normal. 

Dallas  

is 

12 

IB 

°F. 

12 
19 
21 

•F. 

35.4 
36.0 

°F. 
44.4 
4x.r. 
49.9 

°F. 
-0.5 
+  1.7 
+  2.0 

Inches. 
1.9S 
1.97 
.81 

Aider. 

-0.  74 
-  .ti7 

-1.65 

10 

21 

39.2 

49. 6 

+3.S 

1.92 

-2. 39 

Waco  

u 

lt> 

22 

16,0 

51.2 

+3.1 

I.3.S 

-  .55 

Nacogdoches  

19 

26 

34.9 

47.4 

—  .8 

4.  s5 

+  2. 11 

Austin  

3 

41.6 

51.4 

+2.7 

.81 

-l.t.7 

3 

IB 

42.1 

54  4 

+  .8 

1.34 

-1.09 

Average  

11 

3,1 

49.6 

+  1.6 

1.88 

-  .83 

E  BBRUARY. 


Dallas  

n 

15 

32.6 

46.0 

+  1.4 

2.23 

53 

9 

19 

37.1 

5S.0 

+  1.9 

2.61 

+ 

49 

Ilearne  

23 

37.2 

49.4 

-  .5 

4.  L'_ 

+  2 

40 

Palestine  

M 

3K7 

l.s.ti 

-2.4 

3!  06 

45 

Waco  

8 

20 

37. 3 

50.8 

-  .8 

2.65 

+ 

72 

Nacogdoches  

10 

20 

30.7 

48.2 

-  .4 

1.78 

 2 

09 

Austin  

8 

u 

43. 9 

52.1 

-  .6 

1.29 

59 

Victoria  

5 

28 

44.3 

54.4 

+  .4 

2.01 

+ 

19 

Average  

8 

38.5 

51.0 

-M 

2.48 

+ 

15 

MARCH. 

Dallas  

11 

25 

38.9 

50.8 

-4.8 

3.24 

+  0 

09 

Corsicana  

5 

27 

39.7 

49.9 

—7.6 

2. 10 

-1 

25 

Ilearne  

2 

28 

43.4 

55.4 

-2.3 

1.97 

64 

Palestine  

s 

28 

44.1 

53.4 

-4.2 

1.24 

 2 

74 

Waco  

27 

43.2 

57.5 

—1.1 

2.95 

09 

Nacogdoches  

3 

27 

44.0 

54.3 

-3.2 

1.63 

 2 

82 

Austin  

1 

32 

47.8 

56.  s 

-3.4 

2.  47 

+ 

25 

Victoria  

1 

31 

50.5 

61.0 

-1.7 

2. 24 

+ 

7  2 

Average  

3.5 

44.0 

55.0 

-3.54 

2.23 

94 

A  comparison  of  the  principal  points  shown  in  Tables  VIII  and 
X  indicates  the  relative  severity  of  the  two  seasons,  especially  in 
the  columns  showing  absolute  minimiun  and  average  minimum 


30 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


temperatures  and  departures  from  normal.  The  records  for  February 
are  especially  significant.  In  1905  this  month  was  unusually  cold 
throughout  the  State.  The  absolute  minimum  for  the  five  local- 
ities considered  in  that  year  was  2°  F.  at  Dallas  and  the  average  mini- 
mum was  8.3°  F.  below  that  occurring  in  1906.  In  1905  the  mean 
average  temperature  for  the  month  was  10.6°  F.  below  the  normal 
while  in  1906  it  was  but  0.12°  F.  below  normal.  It  was  during  this 
month  of  extreme  cold  with  excessive  rainfall  in  1905  that  the  great- 
est mortality  among  weevil  stages  occurred. 

HIBERNATION  SHELTER  OTHER  THAN  BOLLS  WITHIN  THE  FIELD. 

During  an  ordinary  season  it  can  not  be  doubted  that  a  large 
majority  of  the  weevils  which  survive  find  some  other  shelter  than 
the  bolls  hanging  upon  the  plants.  It  is  not,  however,  as  easy  a 
matter  to  find  weevils  in  rubbish  scattered  upon  the  ground  as  in 
bolls.  It  is  necessary  to  collect  the  rubbish  very  carefully  and  sift 
it  over  cloth  or  paper  to  separate  the  weevils  from  the  trash.  In 
this  way  it  has  been  found  that  weevils  hibernate  extensively  in  the 
leaf  and  grass  rubbish  distributed  throughout  the  field.  Naturally 
the  cleaner  the  field  in  the  fall  the  smaller  will  be  their  chances  of 
finding  favorable  shelter  during  the  winter. 

Standing  trees  are  a  common  sight  in  cotton  fields,  and  while  the 
records  of  weevils  found  hibernating  under  bark  are  but  few  they 
are  sufficient  to  indicate  that  these  trees  may  be  a  rather  important 
factor  where  they  occur  in  considerable  numbers.  Where  the 
Spanish  moss  (Tillandsia  usneoides)  (PI.  II,  fig.  1)  occurs,  as  in  the 
bottom  lands  in  the  coast  section  of  Texas  and  in  the  southern  por- 
tions of  the  Gulf  States,  weevils  find  exceptionally  favorable  shelter 
within  this  moss.  On  January  18  Mr.  J.  D.  Mitchell  cut  down  a 
moss-covered  tree  growing  in  a  large  cotton  field  in  the  vicinity  of 
Victoria,  Tex.  Between  400  and  500  pounds  of  moss  growing  on 
this  tree  was  collected  and  examined  very  carefully.  Three  living 
specimens  of  the  boll  weevil  were  found.  On  February  5,  1907,  a 
similar  experiment  was  tried.  One  thousand  pounds  of  moss  was 
obtained  from  a  tree  standing  in  the  midst  of  cotton  fields.  The 
moss  was  situated  from  7  to  15  feet  above  the  ground.  Among  a 
large  number  of  other  insects  found  hibernating  in  the  moss  there 
were  ten  living  boll  weevils.  The  weevils  seem  to  prefer  the  festoons 
of  green  hanging  moss  to  the  bunches  of  dead  matted  moss  (PI.  II, 
fig.  2). 

The  turnrows  and  ditches  throughout  the  fields  and  the  fence  rows 
(PI.  I,  fig.  2)  surrounding  them  present  exceptionally  favorable  con- 
ditions for  successful  hibernation.  It  has  been  noticed  frequently 
that  early  in  the  season  the  most  severe  injury  may  occur  on  the 
edge  of  a  field  adjoining  a  fence  row  where  weeds  and  grass  abound. 


Bui.  77,  Bureau  of  Entomology,  U.  S.  Dept.  of  Agriculture 


Plate  I. 


Weather-Recording  Apparatus  and  Fence-Row  Shelter. 

Fig.  1.— Weather  apparatus  used  in  recording  temperature  and  humidity  conditions.   Fig.  2.— 
Typical  weedy  fence  row.  affording  excellent  shelter  for  weevils.    (Original.  | 


Bui.  77,  Bureau  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


Plate  II. 


Favorable  Shelter  Conditions  in  and  around  Fields. 

Fig.  l.— Cotton  field  adjoining  grove  of  trees  laden  w  ith  Spanish  moss  |  JHUandsia  umeoides), 
Fig.  2.— Near  view  01  moss.  Fig.  3. — Cotton  stalk  having  many  hoi  Is  infested  hy  weevils 
at  hihernation  time.  (Original.) 


SHELTER  DURING  HIBERNATION. 


31 


One  fact  should  ho  emphasized  in  regard  to  practically  all  classes 
of  shelter  which  have  been  mentioned  as  occurring  within  cotton 
fields,  i.  e.,  that  it  is  possible  as  a  rule  to  destroy  or  remove  practi- 
cally all  of  them.  Undoubtedly  the  burning  of  cotton  stalks,  weeds, 
grass,  and  other  rubbish  is  the  easiest  and  most  effective  method  of 
destruction  where  it  can  be  practiced.  Next  to  this  in  importance 
would  be  the  destruction  of  the  stalks  by  a  stalk  chopper  and  plowing 
under  all  the  rubbish.  In  the  latter  case  it  must  be  stated  that 
many  weevils  which  may  be  buried  to  an  average  depth  of  2  inches 
will  be  able  to  escape  through  the  soil  and  may  then  find  shelter 
around,  if  not  within,  the  field. 

HIBERNATION   SHELTER  OUTSIDE  OF  COTTON  FIELDS. 

Unquestionably  timber  fringes  skirting  cotton  iields  are  exceed- 
ingly important  because  of  the  shelter  which  the  fallen  leaves  and 
undergrowth  provide  for  weevils  during  the  winter.  The  conditions 
to  be  found  here  are  so  exceedingly  favorable  that  a  majority  of 
planters  seem  to  recognize  that  the  most  severe  infestation  of  young 
cotton  in  the  spring  may  be  expected  to  occur  near  such  timber. 
Where  the  moss  (PI.  II,  fig.  1)  occurs  abundantly  it  is  second  only 
in  importance  to  the  fallen  leaves  as  a  shelter  for  weevils.  The  fact 
that  weevils  have  been  taken  early  in  the  spring  upon  trees  at  a  dis- 
tance as  great  as  2  miles  from  a  cotton  field  shows  the  extent  to 
which  they  may  ] >< >>^i  1  >l \  scatter  during  the  fall  or  seek  for  cotton 
during  the  spring.  The  planter  need  not.  however,  be  alarmed  by 
these  facts,  inasmuch  as  it  is  certain  that  but  few  weevils  hiber- 
nating away  From  tie  immediate  vicinity  of  cotton  fields  will  sur- 
vive to  find  food  supply  upon  emergence. 

Cornfields  adjoining  cotton  or  cornstalks  scattered  throughout 
cotton  iields  may  shelter  many  weevils.  This  was  first  noticed  by 
Mr.  K.  A.  Schwarz  at  Victoria  in  the  winter  of  1901-2  and  has  since 
heen  corroborated  by  a  number  of  observers.  Several  examina- 
tions have  been  made  of  haystacks  in  the  vicinity  of  cotton.  This 
is  a  ta>k  quite  comparable  with  that  of  seeking  for  the  proverbial 
needle  and  it  is  not  surprising  that  the  results  have  been  very  meager. 
The  fact,  however,  that  traces  of  weevils  have  been  found  in  these 
examinations  indicates  that  weevils  may  hud  shelter  under  such 
conditions. 

Farmyards,  seed  houses,  barns,  ginneries,  and  oil  mills  also  afford 
exceptionally  favorable  shelter  for  weevils.  Especially  in  ginneries 
and  seed  houses  (PL  III,  fig.  1)  the  weevils  become  concentrated 
with  the  concentration  of  the  cotton  or  seed  and  frequently  may  be 
found  in  large  numbers  within  or  around  these  buildings.  In  con- 
nection with  this  subject  the  reader  is  referred  to  a  fuller  discus- 


32 


HIBERNATION  OF  THE  COTTOX  BOLL  WEEVIL. 


sion  of  the  significance  of  ginneries  and  oil  mills  in  the  distribution 
of  weevils  and  of  the  methods  recommended  for  controlling  them 
which  may  be  found  in  Farmers'  Bulletin  No.  209  of  the  Department 
of  Agriculture,  "  Controlling  the  Cotton  Boll  Weevil  in  Cotton  Seed 
and  at  Ginneries."  Numerous  observations  have  shown  that  weevils 
have  been  taken  into  new  localities  through  the  agency  of  shipments 
of  cotton  seed  and  cotton-seed  hulls  from  ginneries  and  oil  mills 
handling  infested  stock.  Definite  observations  have  been  made 
showing  that  living  weevils  may  occur  in  cotton  seed  at  planting 
time.  While  it  is  probable  that  few  would  survive  in  a  large  mass 
of  seed  it  is  certain  that  some  might  do  so  and  be  distributed  in 
the  planting  of  the  seed. 

Table  XI. — Experiments  of  1904  to  1906  to  test  hibernation  in  cotton  seed. 


Locality. 


Terrell,  Tex. . . 

Do  

Do  

Corsicana,  Tex. 
Calvert,  Tex. . . 

Do  

Do  

Victoria,  Tex. . 

Do  

Do  

Do  

Do  

Do  


Total. 


"When 
put  in 
hiberna- 
tion. 


1904. 
Nov.  13 
Nov.  30 
Dec.  15 
Nov.  14 
Nov.  15 
Nov.  30 
Dec.  15 
Nov.  10 
Nov.  17 
Nov.  25 
Dec.  1 
Dec.  8 
Dec.  15 


1905. 

Dallas,  Tex   Nov.  1 

Do  I  Nov.  18 

Do   Dec.  4 

Do   Dec.  15 

Total  


Victoria,  Tex. 
Do  


Nov.  7 
...do  


Do   Nov.  13 

Do   Nov.  30 

Do   Dec.  11 


Weevils 
put  in 
hiberna- 
tion. 


200 
200 
250 
150 
200 
200 
200 
200 
200 
200 
200 
200 
200 


When 
exam- 
ined. 


1905. 
Apr.  20 
Apr.  21 
Apr.  22 
Apr.  19 
Apr.  7 
Apr.  8 

..do  

Apr.  3 

..do  

Apr.  1 
Mar.  31 
Mar.  29 
Mar.  28 


Weevils 
found 
alive. 


2,600 


100 
200 
200 
900 


1,400 


100 
100 
100 


Total. 


190G. 

Apr. 

28 

Apr. 

30 

May 

3 

May 

4 

Apr. 

2 

Apr. 

7 

Apr. 

3 

...do 

Apr. 

5 

o2 


Weevils 
found 
dead. 


154 
139 
170 
127 
152 
176 
142 
130 
144 
150 
115 
149 
123 


100 
181 

802 


1,295 


93 


97 
100 


479 


a  On  January  27  47  dead  and  18  living  weevils  were  removed,  and  on  March  4  4  dead  and  1  living  weevils 
were  removed. 


While  the  number  and  percentage  of  weevils  surviving  in  these 
experiments  is  very  small  indeed,  the  fact  that  some  do  survive  is  the 
special  point  having  significance.  The  occasional  occurrence  up  to 
planting  time  of  living  weevils  among  seed  from  infested  localities 
is  alone  sufficient  justification  for  every  quarantine  restriction  which 
lias  been  placed  upon  cotton  seed  and  other  cotton  products  by 
uninfested  territory. 

The  Mexican  entomologist  Prof.  L.  de  la  Barreda,  under  the  direc- 
i  ion  of  Prof.  A.  L.  Herrera,  of  the  Comision  de  Parasitologia  Agricola, 


HIBERN  ATION    KXPKHI MKNTS  IN   SMALL  CAGES. 


33 


has  made  some  very  pertinent  observations  on  the  occurrence  of 
boll  weevils  in  cotton  seed  intended  for  planting.  a  In  January,  1903, 
this  entomologist  examined  a  number  of  sacks  of  seed  received  from 
the  infested  area  of  Texas  for  planting  in  the  Laguna  region  in  Mexico. 
Six  sacks  from  one  consignment  were  selected.  In  these,  12  living 
weevils  were  found,  together  with  56  dead  ones.  Later  examinations 
were  made  of  a  number  of  shipments  of  seed  from  the  infested  por- 
tions of  the  United  States.  In  every  ease  living  weevils  were  found. 
This  work  was  done  in  the  month  of  January.  These  observations 
show  clearly  the  real  danger  that  exists  in  the  shipment  of  cotton 
seed  from  infested  localities  to  those  where  the  weevil  does  not  occur. 

HIBERNATION  EXPERIMENTS  IN  SMALL  CAGES. 

In  many  ways  it  is  possible  to  obtain  more  accurate  data  upon 
hibernation  of  weevils  through  cage  experiments  than  through  field 
observations.  In  the  cages  conditions  may  be  prepared  which  are 
typical  of  those  to  be  found  in  the  fields.  The  number  of  weevils 
within  a  given  space  can  be  largely  increased  without  overcrowding, 
so  far  as  the  possibility  of  their  finding  shelter  is  concerned.  The 
action  of  the  weevils  in  seeking  and  in  leaving  shelter  can  be  deter- 
mined more  accurately  in  cages  than  in  the  field.  The  food  condi- 
tions may  be  varied  to  represent  various  field  conditions  and,  finally, 
knowing  definitely  the  number  of  weevils  placet!  under  certain  con- 
ditions, it  is  possible  to  follow  them  closely  enough  to  determine  with 
a  great  deal  of  accuracy  the  proportions  surviving.  From  a  com- 
parison of  the  results  obtained  under  various  experimental  condi- 
tions those  conditions  which  are  most  favorable  as  well  as  those  which 
are  least  favorable  to  successful  hibernation  may  be  determined  with 
considerable  certainty.  In  all  of  our  experimental  work  of  this  nature 
the  cage  results  have  been  checked  so  far  as  has  been  possible  by 
field  observations. 

With  the  continued  study  of  the  boll-weevil  problem  the  necessity 
for  increasingly  comprehensive  experiments  upon  hibernation  has 
become  apparent.  The  work  thus  shows  from  year  to  year  a  growth 
in  complexity  with  the  constant  purpose  of  increasing  the  accuracy 
of  results  by  making  the  experimental  conditions  conform  as  closely 
as  is  possible  to  field  conditions.  In  the  early  stages  of  the  work  the 
hibernation  cages  were  small  and  portable.  Some  were  placed  out 
of  doors  where  they  would  be  fully  exposed  to  prevailing  climatic 
conditions;  others  were  placed  in  the  shelter  of  buildings  or  under 
similar  conditions  where  the  favorable  nature  of  the  shelter  provided 
might  be  determined. 


a  Boletm  de  la  Oomision  de  Parasitologia  Agricola,  vol.  2,  No.  2,  pp.  45  to  61, 
90317— Bull.  77—09  3 


34 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


CAGE  EXPERIMENTS  OF  1902-3. 

In  the  experiments  made  during  the  season  of  1902-3  most  of  the 
weevils  used  were  collected  in  the  field  at  Victoria,  Tex.,  about  the 
middle  of  December.  Some,  however,  were  reared  weevils  which 
during  the  months  of  September  and  October  previous  had  become 
adult.  They  were  confined  in  boxes  and  jars  covered  with  cheese 
cloth.  Various  kinds  of  rubbish  were  placed  in  the  cages,  some  of 
which  were  placed  in  the  fields  and  some  in  a  building. 

These  cages  were  all  examined  between  April  15  and  30,  1903. 
Among  the  25  lots  tested,  including  356  weevils,  it  was  found  that 
an  average  of  about  11  per  cent  had  survived.  None  of  those  which 
were  adult  before  November  1  was  living  on  April  15,  while  nearly 
16  per  cent  of  those  taken  in  the  field  about  the  middle  of  December 
were  still  alive  on  April  27.  A  slightly  higher  percentage  had  sur- 
vived in  the  inside  tests,  and  it  appears  that  a  considerable  degree 
of  dryness  favored  survival.  One-half  of  all  the  weevils  surviving 
were  found  in  the  folds  of  dead  banana  leaves  on  April  15,  while  the 
balance  were  scattered  among  hay,  dried  cotton  leaves,  empty  bolls, 
and  in  or  under  earth. 

CAGE  EXPERIMENTS  OF  1903-4. 

During  the  season  of  1903-4  450  weevils  were  tested  in  lots  of 
about  50  each.  From  October  21  to  December  16  one  or  more  lots 
were  started  each  week,  part  of  them  being  placed  outdoors  and 
part  indoors.  In  addition  to  the  confinement  of  adults,  about  400 
infested  squares  were  picked  from  the  ground  about  November  15 
and  kept  until  the  following  March.  These  squares  were  examined 
on  March  18.  It  was  found  that  most  of  the  stages  had  perished 
while  yet  larvae.  Nearly  one-fifth  of  the  squares  contained  dead 
adults.  In  the  lot  among  128  stages  there  was  one  adult  which  was 
still  alive. 

Examination  in  April,  1904,  accounted  for  all  but  15  of  the  450 
weevils  confined,  but  one  weevil  was  found  alive,  and  that  one  was 
placed  in  hibernation  on  October  29  in  a  cage  out  of  doors.  The 
results  during  this  season  seem  to  contradict  in  some  respects  those 
obtained  during  the  preceding  year,  which  indicated  the  favorable 
nature  of  inside  shelter. 

CAGE  EXPERIMENTS  OF  1904-5. 

The  work  of  the  season  of  1904-5  was  planned  to  include  a  number 
of  localities  representing  in  a  general  way  the  various  portions  of  the 
weevil-infested  area.  In  all  eases  the  cages  consisted  of  boxes  about 
1  by  2  feet  in  size  and  covered  with  14-mesh  galvanized-wire  screen- 


EXPERIMENTS  1 2s   SMALL  CAGES. 


35 


ing.  These  were  all  placed  out  of  doors  at  various  dates  between 
November  .*}  and  December  15,  1904.  The  examinations  were  made 
during  April,  1<)()5. 

Tahi.k  XII.— Summary  of  hibernation  >  xpt rinu nts.  1904-5. 


Locality. 


Terrell.  Tex. . . 
Paris,  Tex  

krilh\  lllr.  LA. 

Corsicana.  TCQI 
Calvert.  Tex... 
Victoria.  TttX.. 


715 
two 

IV 

:,72 
.500 
<«M) 


244 
2.54 
229 
27  s 
240 
Mil 


Total  3.N2U  1.S46 


(I  Ills 

0  116 

ii  120 

n  ir.7 

o  s.} 

11  I'M, 

11  |T85 


Total  number  of  weevils  found— 


(is  1.1 

58  14 

f,s  II) 

CO  23 

17 

I'M) 


I'M 


111 


'.r_>  35 


51 


54 


I  1  M 


is 


12 


T5  25 


19 


12 


32  12 


The  most  striking  point  shown  in  this  table  is  the  fact  that  no 
weevils  survived  except  at  Victoria.  Even  there  the  percentage  was 
very  small.  I  ndouhtedly  from  to  10  per  cent  of  the  weevils  placed 
in  the  cages  must  have  escaped  through  the  wire  before  the  season 
became  cold  enough  for  all  to  hibernate.  The  explanation  for  the 
death  of  all  weevils  confined  north  of  Victoria,  Tex.,  may  be  found 
in  the  exceptionally  severe  climatic  conditions  occurring  during  this 
season.  These  have  already  been  indicated  in  Table  VIII,  page  27. 
It  should  be  stated,  however,  that  while  weevils  were  scarce  in  the 
spring  of  1905  in  all  of  these  localities  they  were  not  exterminated 
in  Texas  except  at  Paris.  At  this  place  examinations  made  during 
the  season  of  1905  failed  to  show  any  weevils  in  a  field  which  had 
been  quite  heavily  infested  late  in  the  season  of  1904. 

HIBEBNATION  EXPERIMENTS  IN   SMALL  CAGES,  1905-6. 

Tests  were  made  at  Dallas,  Calvert,  and  Victoria,  Tex.,  representing 
the  northern,  central,  and  southern  sections  of  the  infested  area. 
Owing  to  the  increased  complexity  of  the  experiments  and  the  more 
valuable  character  of  the  results  obtained,  it  seems  advisable  to 
present  the  data  in  a  somewhat  more  detailed  manner. 


36  HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


Table  XIII. 


-Summary  of  hibernation  experiments  in  boxes  at  Dallas,  Calvert,  and 
Victoria,  Tex.,  in  1905-6. 


DALLAS. 


Kind  of  rubbish. 


Out- 
doors 
or  in- 
doors. 


Wee- 
vils 
put 
in. 


When  ex- 
amined. 


Number  of  wee- 
vils found- 


Alive.  Dead 


Per- 
centage 
alive. 


Remarks. 


Nov.  1 

Corn  shucks,  grass, 

cotton  leaves. 

Do... 

Cotton  leaves  

Do 

 do  

Do... 

Sack  of  cotton  seed... 

Nov.  17 

Grass,  leaves,  rubbish . 

Do 

 do  

Nov.  18 

Cotton  seed  

Nov.  26 

Only  grass  

Do... 

Grass,  seed,  cotton. .. 

Dec.  4 

Cotton  seed  

Dec.  11 

Corn  shucks,  leaves. . 

Do 

 do  

Dec.  15 

Cotton  seed  

Total. 


Out... 

In  

In  

In  

Out... 

In  

In  

Out. . . 

In  

In  

Out... 

In  

In  

fOut... 
[In  


100 

100 
100 
100 
100 
100 
200 
200 
200 
200 
200 
200 
900 


600 
2, 100 


1906. 
Apr.  27 

..do.... 
..do.... 
Apr.  28 
Feb.  19 
..do.... 
Apr.  30 
May  1 
..do.... 
May  3 
..do.... 
May  1 
May  4 


92 

80 
64 
92 
82 
87 
160 
165 
165 
181 
140 
195 
862 


479 
1,886 


0.5 
0.0 


In  chicken  house. 
In  seed  house. 
Do. 

Do. 
Do. 

Do. 


300  in  each  of  3  sacks. 


CALVERT. 


1905. 

1906. 

Nov.  7 

Corn  shucks,  grass, 

In 

100 

Apr  18 

0 

98 

0 

cotton. 

Do... 

 do  

Out. . . 

94 

...do  

1 

45 

1 

Nov.  27 

 do  

In  . 

205 

...do  

0 

205 

0 

Do 

 do  

Out... 

200 

Apr.  19 

40 

145 

20 

/Out... 

294 

41 

190 

14.0 

Total  

\In  

305 

0 

303 

0.0 

VICTORIA. 


1905. 

Nov.  5 

Nov.  7 

 do  

Do... 

 do  

Nov.  13 

 do  

Do... 

 do  

Nov.  30 

 do  

Do... 

 do  

Dec.  11 

 do  

Total  

Total  of  3  local- 

ities  

1906. 

Out... 

100 

Apr.  6 

2 

43 

2 

Out... 

100 

Apr.  7 

1 

23 

1 

In 

100 

...do  

0 

73 

0 

Out... 

100 

Apr.  4 

4 

53 

4 

In 

100 

Apr.  5 

0 

97 

0 

Out... 

100 

...do  

1 

39 

1 

In 

100 

...do  

0 

94 

0 

Out... 

100 

Apr.  7 

3 

51 

3 

In.  . 

112 

...do  

4 

100 

3. 57 

fOut. . . 

500 

11 

209 

2.2' 

Hn  

412 

4 

364 

.97 

fOut. . . 

1,394 

55 

878 

3.9 

Hn  

2,817 

4 

2, 553 

.14 

In  the  small-cage  experiments  of  1905-6  but  three  localities  were 
tested.  In  the  26  experiments  were  placed  4/211  weevils,  of  which 
number  1,394  were  out  of  doors  and  2,817  indoors.  In  only  one 
cage  did  weevils  survive  within  doors,  and  that  was  at  Victoria, 
where  it  would  seem  that  such  protection  was  least  needed.  The 
two  most  striking  results  were  the  small  survival  at  Dallas  and  the 
remarkably  large  survival  in  one  of  the  outdoor  experiments  at 
Calvert.    In  the  outdoor  tests  an  average  of  3.9  per  cent  survived, 


IITr.ERXATTOX  EXPERIMENTS  IX  SMALL  CAGES. 


37 


while  in  the  others  hut  0.14  per  eent  survived.  In  an  average  of 
all  tests  the  BUrvival  was  1.4  per  cent. 

The  nature  of  the  shelter  failed  to  show  any  significant  influence 
in  these  small-cage  experiments. 

The  relative  favorahleness  of  outside  conditions  is  shown  in  the 
following  table  hy  a  comparison  of  the  data  in  each  of  the  three 
localities.  This  table  does  not  include  the  experiments  with  cotton 
seed: 


Table  XIV.  —  Comparison  of  turvival  records  outdoors  and  indoors  for  thru  T<  ECU 

localitiis  in  1 905-6. 


Locality. 

Outride. 

Inside. 

Weevils 
pal  in 
biberna- 
tion. 

Weevils  survived. 

Weevils 
put  in 
hlberna- 
tion- 

Weevils  survived. 

Number. 

Percent- 
age. 

Number. 

Percent- 
age. 

Victoria,  Tex  

Calvert,  Tex  

Dallas,  Tex  

Total  

500 
294 
000 

11 

41 

3 

2.2 
14.0 
.5 

412 
:{().-, 
2.100 

4 

0 
0 

0.07 

0 

0 

1,394 

55 

3.9 

2,8.7 

4  1         0. 14 

During  this  season  it  is  very  evident  that  in  all  localities  outdoor 
conditions  were  decidedly  more  favorable  for  successful  hibernation. 
Upon  the  average  the  survival  out  of  doors  was  twenty-eight  times 
as  successful  as  in  the  tests  made  indoors. 

Grouping  the  experiments  according  to  fifteen-day  periods  from 

November  1  to  December  15,  when  they  were  instituted,  the  most 
favorable  time  for  entering  hibernation  seems  to  be  indicated. 


Tahlk  XV.  -Comparative  favorable  nrss  of  periods  for  niter imj  hibernation,  1905. 


Locality. 

Period. 

Total 
survival. 

Nov.  1-15, 1905. 

Nov.  15-30,  1905. 

Dec.  1-15,  1905. 

Num- 
ber. 

Per 
cent. 

Weevils 
put  in 
hiber- 
nation. 

Weevils 
survived. 

Weevils 
put  in 
hiber- 
nation. 

Weevils 
survived. 

Weevils 
nut  in 
hiber- 
nation. 

Weevils 
survived. 

Num- 
ber. 

Per 

cent. 

Num- 
ber. 

Per 
cent. 

Num- 
ber. 

Per 
cent. 

Victoria,  Tex  

Calvert,  Tex  

500 
194 
300 

7 
1 
0 

1.4 

.5 
.0 

200 
405 
600 

1 

40 

3 

0.5 
10.0 
.5 

212 

7 

3.3 

15 
41 

3 

1.60 
6.80 
.23 

Dallas,  Tex  

Total  

400 

0 

-  0 

994 

8 

•' 

1,205 

44 

3.7 

612 

7 

1.1 

59 

2. 10 

This  table  does  not  include  the  experiments  in  cotton  seed.  The 
comparisons  show  that  during  the  fall  of  1905,  November  15  to  30 
was  more  favorable  than  either  an  earlier  or  later  period  at  Calvert 


38 


HIBERNATION"  OF  THE  COTTON  BOLT,  WEEVIL. 


and  Dallas,  while  at  Victoria  the  period  between  December  1  and  15 
was  more  favorable. 

The  shelter  conditions  within  which  weevils  survived  was  also 
determined  in  these  experiments,  and  the  principal  points  are  shown 
in  the  following  table,  which  again  does  not  include  cotton-seed  tests : 


Table  XVI. — Shelter  in  which  surviving  weevils  were  found  in  April  and  May,  1906. 


Locality. 

Bermuda 
grass  and 
hay. 

Excelsior. 

Paper. 

Banana 
leaves. 

Corn 
shucks,  old 

cotton 
stalks,  and 

bolls. 

Total. 

Victoria,  Tex  

Calvert,  Tex  

5 

4 

1 

1 

4 

41 

15 
41 
3 

Dallas,  Tex  

3 

Total  

8 

4 

1 

1 

45 

59 

This  shows  the  favorable  nature  of  old  corn  and  cotton  stalks, 
among  which  the  survival  in  one  cage  at  Calvert  was  surprisingly 
large.  It  also  indicates  that  weevils  may  survive  in  varied  shelter, 
and  that  in  all  probability  the  temperature  and  moisture  conditions 
experienced  may  be  as  important  as  the  nature  of  the  shelter  in 
determining  survival. 

LARGE-CAGE  EXPERIMENTS,  KEATCHIE,  LA.,  1905-6. 

With  the  work  of  1905-6  a  change  was  made  in  the  method  of 
carrying  on  the  hibernation  experiments.  Instead  of  using  numer- 
ous small  boxes  in  a  number  of  places,  large  screen-covered  cages  were 
utilized  in  the  fields  at  Keatchie,  La.,  and  Dallas,  Tex.  The  Keatchie 
cage  (PL  III,  fig.  2)  was  constructed  under  the  direction  of  Mr. 
Wilmon  Newell,  secretary  of  the  State  crop  pest  commission  of 
Louisiana  and  special  field  agent,  cooperating  in  the  boll  weevil 
investigations.  It  was  probably  the  largest  structure  of  its  kind 
that  has  ever  been  built  for  an  entomological  investigation.  The 
interior  was  divided  by  partitions  into  eighteen  sections.  The 
shelter  conditions  for  the  weevils  and  the  dates  upon  which  weevils 
were  inclosed  were  planned  to  represent  the  extremes  of  field  condi- 
tions as  to  shelter  and  date  of  entrance  into  hibernation.  The  gen- 
eral plan  of  the  experiment  is  shown  in  the  first  section  of  Table 
XVII,  and  in  the  last  section  are  included  the  emergence  records  for 
the  cage. 

Before  entering  upon  a  discussion  of  the  work  at  Keatchie  special 
credil  should  be  given  Mr.  Wilmon  Newell  and  his  assistant,  Mr.  J.  B. 
Garret  1,  who  were  particularly  concerned  in  the  execution  of  the 
work  al  Keatchie.  Much  work  has  also  been  done  by  Mr.  W.  D. 
Hunter  upon  the  reports  of  the  Keatchie  experiments  in  arranging 
the  data  so  as  to  show  the  most  significant  facts. 


Bui.  77.  Bureau  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


Plate  III. 


Seed  House  and  Hibernation  Cage,  Keatchie,  La. 

Fig.  1.— -Seed  house  opposite  which  the  first  sign  of  weevil  work  was  found  at  Keatchie,  La.,  in 
190-").    Fig.  "2.  — Larue  cage  built  lor  hibernation  experiments  in  190")-(i.  (Original.) 


T  \  BLE 


LAlKilX  ACK  EXPERIMENTS,  KKATCHIE,  LA.,  1005-ft.  39 
XVII. — Summary  of  installation  and  emergence  records  in  cage  at  Keaichie.  La. 


Installation  records,  1905. 


PJ 


Louisiana. 

2..  ...do  

3..  ...do  

4  do  

5..  ...do  

6..I  Texas  

7..  ...do  

8..  ...do  

9..  ...do  

10..  ...do  

11..  ...do  

12..  ...do  

13..  Louisiana. 

14..  Texas  

15.  J. ..do  

16  do  

17  Louisian  i . 
18.. I... do  


Nov.  29  1,200 


Nov.  26  1,000 
..do   1.000 


...do  

...do  

Nov.  23 

Nov.  29 
Nov.  25 

...do  

...do  

...do  

Nov.  n 

Dec.  In 


1,000 
1,000 
1,000 

2,100 
I.. 500 
1,000 
1,000 
1,000 
1,000 
1,000 


Dec.    3  4,000 

...do   4,000 

Dm.  i  1,000 

Nov.  2S  1.000 

Nov.  18  1.000 


Shelter  in  cage  section. 


Brush,  leaves,  moss,  stamps,  logs; 
stalks  removed. 

Same,  but  stalks  standing  

Cotton  seed  piled;    plants  left 

standing. 
Same,  but  seed  left  uncovered. . . 

Absolutely  bare  

Ordinary  field  

Stalks,  grass,  etc.: 

Same  as  1  

Same  as  2  

Same  as  3  

Same  as  4  

Same  as  5  

Same  as  6  

Stalks  left;   leaves,  etc.  added; 
shaded. 

Same  as  13,  but  not  shaded  

Same  as  14  

...do  

...do  ;. 

Check  on  13;  stalks,  grass,  leaves, 

not  shaded. 


K mergence  records,  1906. 


March. 


April. 


Totals  and  averages.  25,  XX) 


■ 

d 

a 

oj 

a 

8 

8 

8 

- 

■ 

§ 

§ 

u 

y 

5 

S3 

2 

0. 166 

3 

0. 25 

4 

0. 33 

0 

7 

.  7 

10 

1.0 

1 

.  1 

4 

.  4 

0 

2 

.2 

5 

.5 

0 

.1 

0 

5 

!5 

18 

1.8 

4 

.4 

2 

.09 

17 

.81 

16 

.76 

2 

.  14 

33 

2.2 

15 

1.0 

2 

.2 

9 

.9 

3 

.3 

1 

.2 

15 

1.5 

0 

0 

10 

1.0 

4 

.4 

0 

17 

1.7 

12 

1.2 

1 

.1 

2 

.2 

1 

4 

.1 

29 

.72 

17 

.42 

9 

.22 

94 

2.35 

28 

.7 

1 

.1 

15 

1.5 

5 

.5 

4 

.4 

17 

1.7 

10 

1.0 

0 

15 

1.5 

8 

.8 

38 

.18 

311 

137 

.53 

May  1-14. 


Installation  records.  1905. 


1 

">-~ 

-.  - 

1  — 

r 

*I 

M 

■tion  n 

•  a 
u  8 

-  t 
~  1 

S| 

1 

I 
/. 

1. . 

Louisiana. 

Nov. 

2 

...do  

Nov.  2,5 

3.. 

...do  

...do  : 

4.. 

...do  

...do  

5. . 

...do  

...do  

6.. 

Texas 

Not.  n 

7.. 

...do  

Nov.  2(.* 

8.. 

...do  

Nov.  28 

9.. 

...do  

...do  .. 

10.. 

...do  

...do  

11.. 

...do  

...do  

12.. 

...do   . 

Nov.  23 

13.. 

Louisiana. 

Dec.  IS 

14.. 

Texas 

Dec.  3 

15.. 

...do  

...do  

16.. 

...do  

Dec.    8  | 

17.. 

Louisiana. 

Nov.  28 

18.. 

...do  

Nov.  18 

I 

i-  K 


1,200 
1,(K)0 

1,000 

1,000 

1.IHN) 

1,000 

2, 100 
1,500 
1.000 
1,000 
1.000 
1.000 
1.000 

4,000 
l.OOU 
1,000 
1,000 
1,000 


Totals  and  averages.  25,800 


Brush,  lea\ts,  moss,  stumps, 

logs;  stalks  remo\  e.|. 
Same,  but  stalks  standingv 
Cotton  seed  piled;  plants  left 

standing. 
Same,  but  seed  left  uncovered. 

Absolutely  bare  

ordinary  field  

Stalks.  L.T.ISS,  etc. : 

Same  as  1  

Same  as  2  

Same  as  3  

Same  as  4  

Same  as  5  

Same  as  6  

Stalks  left;  leaves,  etc.,  added; 
shaded. 

Same  as  13,  but  not  shaded. . . 

Same  as  14  

 do  

 do  

Check  on   13;  stalks, 
leaves,  not  shaded. 


grass. 


K mergence  record*!,  I'.mh;. 

1-a 
%  > 

March  1  to 
May  14. 

2 
li 

a 

d  . 
g-g 

Rank  of  section  1 
on  percent  of surv 

s 

d 
t 

u 

~« 

—  o 

S3  = 

e 

«_  — 

o  E 

Pi  u 

_  B 

r 

f 

9 

0.  75 

26 

2. 16 

11 

17 

5 

1.7 
.5 

25 
6 

2.5 
.6 

9 
16 

7 
2 

.  7 
.  2 
2.7 

8 
4 

38 

.8 
.4 
3.8 

15 
17 

C) 

35 
50 
14 
17 
14 
29 
4 

.66 
3.  33 
1.4 
1.7 
1.4 
2.9 

.4 

44 

64 
17 

22 
26 
55 
8 

2.09 
4.26 
1.7 
2.2 
2.6 
5.5 
.8 

13 
3 
14 
10 

8 

15 

50 
132 
21 
31 

23 

1.25 

3.3 

2.1 

3.1 

2.3 

86 
170 
35 
41 
53 

2.15 

4.25 

3.5 

4.1 

5.3 

12 
4 
7 
5 
2 

487 

728 

2.82 

40  HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 

The  beginning  of  this  work  occurred  so  late  in  November  that  none 
of  the  sections  can  be  considered  as  having  been  placed  in  hiberna- 
tion early.  Cold  weather  occurred  between  about  November  30  and 
December  3,  during  which  time  the  majority  of  weevils  entered 
hibernation.  Emergence  appears  to  have  begun  on  March  22,  and 
the  last  weevils  emerged  on  June  28.  The  emergence  during  April 
and  May  was  quite  uniform,  while  during  June  it  decreased  rather 
steadily.  In  these  records  no  allowance  has  been  made  for  the  escape 
of  weevils  through  the  wire  on  the  cage.  Using  the  number  placed 
in  the  cage  (25,800)  as  a  basis,  the  728  weevils  which  emerged  con- 
stitute a  survival  of  2.82  per  cent.  It  is  impossible  to  call  attention 
to  all  of  the  many  interesting  points  shown  in  this  table.  Special 
emphasis,  however,  will  be  given  several  points  through  the  rear- 
rangement of  the  significant  data  in  succeeding  tables. 

Since  climatic  conditions  are  primarily  responsible  for  hiberna- 
tion and  the  emergence  of  weevils  therefrom,  the  records  should 
be  studied  in  relation  to  a  chart  of  the  temperature  conditions, 
such  as  is  given  in  figure  1.  No  climatic  records  are  available  for 
Keatchie  previous  to  the  beginning  of  these  observations  upon  March 
15.  The  emergence  of  weevils  may  well  be  shown  in  relation  to  the 
range  in  temperature  upon  the  same  chart.  In  studying  the  effects 
of  temperature  variations  upon  weevil  activity  it  has  been  found 
that  those  temperatures  which  are  about  43°  F.  alone  produce  activity 
among  the  weevils.  Because  of  this  fact  43°  F.  is  regarded  as  the 
starting  point  in  emergence  records,  and  all  temperatures  above  43 
degrees  may  be  spoken  of  as  " effective  temperatures"  upon  the 
following  diagram;  the  average  between  the  maximum  and  minimum 
extremes  for  the  day  is  recorded  as  the  mean  average  temperature. 
While  it  is  probably  true  that  maximum  temperatures  have  a  special 
significance  in  their  effect  upon  emergence  from  hibernation,  and  that 
minimum  temperatures  have  a  special  effect  upon  entrance  into 
hibernation,  it  will  be  more  simple  and  sufficient  in  this  study  to  use 
the  single  line  representing  mean  average  temperature  during  the 
emergence  period. 

From  this  diagram  it  will  be  seen  that  the  emergence  at  Keatchie 
in  1906  occurred  practically  during  four  rather  clearly  defined  periods. 
These  periods  are  separated  by  marked  declines  in  the  mean  average 
temperature.  It  will  be  noticed  that  as  it  became  warmer  following 
these  cold  periods  there  was  an  increased  emergence  of  the  weevils. 
After  the  middle  of  May  so  large  a  proportion  of  the  living  weevils 
had  emerged  that  the  number  recorded  became  gradually  smaller, 
although  the  temperature  rose  still  higher. 

Some  of  the  special  facts  demanding  attention  are  those  relating 
to  the  effect  of  the  various  conditions  of  shelter  upon  the  survival 
of  weevils,  the  relation  of  emergence  to  effective  temperature  in 


LABGE-CAGE  EXPERIMENTS,  KEATCHIE,  LA.,  lOOo-fi. 


41 


various  periods,  the  relation  of  the  time  of  putting  into  hibernation 
to  the  time  of  emergence  therefrom,  the  relation  of  aeeu  inula  ted  elfeet- 


RAINFALL  IN  INCHES 
O        —        •—  r\) 

o     *      §      S  8 

5  ■ 
1 

N  

s 

s 

S 

s 

o     P  ; 
RAINFALL 

—  : —  ro 
ago 

3  /N  ?NCHES 

ive  temperatures  to  emergence,  and  the  longevity  of  the  emerged 
weevils.    These  subjects  will  be  considered  under  succeeding  topics. 

FAVORABLE  CONDITIONS  FOR  HIBERNATION. 


For  a  study  of  favorable  conditions  for  hibernal  ion  those  sections 
have  been  selected  which  are  most  strictly  comparable  in  respect  to 


42 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


the  time  weevils  were  placed  therein,  the  source  of  the  weevils,  and 
the  nature  of  the  shelter.  Practically  one-half  of  the  weevils  used 
were  collected  in  Texas  and  sent  to  Keatchie  for  this  work.  The 
sections  used  in  this  comparison  received  weevils  between  Novem- 
ber 23  and  29. 

Table  XVIII. — Favorable  conditions  for  hibernation  determined  by  rank  in  percentage 
of  weevils  surviving  at  Keatchie,  La.,  in  1905-6. 


Section  num 
ber  in  cage. 


Nature  of  shelter. 


Weevils 
put  in. 


Weevils  survived. 


Number.  Per  cent 


Rank  of 
section. 


6  and  12 

2  and  8. 
1  and  7. 

4  and  10 

5  and  11 

3  and  9. 


Ordinary  field  stalks,  grass,  etc  

Brush,  leaves,  stumps,  logs;  stalks  standing. . . 

Same  as  above,  but  stalks  removed  

Cotton  seed,  piled  but  uncovered;  stalks  stand 

ing  

Absolutely  bare  ground  

Cotton  seed  piled  and  covered;  stalks  left  stand 

ing  


2,000 
2,500 
3,300 

2,000 
2,000 

2,000 


4.65 
3.56 
2. 12 

1.50 
1.50 

1.15 


It  is  evident  that  ordinary  field  conditions  where  stalks  are  allowed 
to  stand  together  with  the  grass  and  leaves  littered  over  the  ground 
are  as  favorable  for  successful  hibernation  as  any  conditions.  It  must 
be  admitted  that  the  shelter  conditions  in  the  bare  sections  (5  and  11) 
are  not  such  as  would  occur  in  a  field  plowed  in  the  fall  because  of  the 
fact  that  the  inclosed  weevils  could  still  find  shelter  in  the  structure  of 
the  cage  itself.  This  will  undoubtedly  explain  the  survival  of  1.5  per 
cent  in  two  sections  having  no  rubbish  on  the  ground.  It  is  apparent, 
however,  that  even  with  this  advantage  of  cage  structure  over  bare 
ground,  slightly  more  than  three  times  this  percentage  of  weevils  sur- 
vived where  ordinary  field  conditions  existed.  Without  the  shelter 
afforded  by  the  cage  this  difference  would  undoubtedly  be  very  much 
greater.  In  9  sections  which  contained  rubbish,  among  15,500  wee- 
vils, 567,  or  3.66  per  cent,  survived.  The  shelter  may  therefore  be 
held  accountable  for  increasing  the  survival  at  least  2.1  per  cent. 
Thus  upon  an  area  where  no  more  than  15  weevils  might  survive  with- 
out protection,  36  at  least  might  be  expected  to  survive  with  the  pro- 
tection. 


EFFECT  OF  ACCLIMATIZATION  UPON  SURVIVAL  AND  EMERGENCE. 

It  has  already  been  mentioned  that  about  one-half  of  the  weevils 
used  in  this  work  were  collected  in  Texas  and  one-half  at  Keatchie,  La. 
In  order  to  determine  whether  this  difference  in  the  geographical  sec- 
1  ion  in  which  the  weevils  developed  might  exert  an  influence  upon 
their  survival  and  emergence  the  records  for  a  number  of  comparable 
seel  ions  are  combined.  These  weevils  were  all  placed  in  hibernal  ion 
between  November  25  and  29,  1905. 


LABGE-CAGE  EXPERIMENTS,  KEATCIIIE,  LA.,  1905-6. 


43 


Tablr  XIX. — Comparison  of  emergence  records  at  Kcatchic,  La.,  for  weevil*  collected 
in  Louisiana  with  those  collected  in  Texas. 


Date. 

Percentage    of  emer- 
gence   during  each 
month    based  upon 
total  emergence  of— 

6.200  wee- 
vils col- 
lected in 

Louisiana. 

6.600  wee- 
vils col- 
lected in 
Texas. 

1906. 

March  

9.09 
33.63 

2s.  isr,u 

7.28 

4.6 

48.6 

{  8>a 

4.6 

April  

May  1-14  

May  15  June  1  

June  2  30  

100.00 

100.0 

Altogether  in  these  sections  110  of  the  Louisiana  weevils  and  173  of 

the  Texas  weevils  emerged,  making  a  percentage  of  total  survival  in 

the  former  case  of  1.77  and  in  the  latter  case  of  2.62,  On  the  whole 
the  Texas  weevils  emerged  slightly  earlier  than  did  those  collected  in 
Louisiana,  hut  the  records  are  too  nearly  >iniilar  to  indicate4  that  such 

would  regularly  be  the  case. 

RELATION   OF   EMERGENCE   To    EFE  KCTIVK   TEM  I'EHATl  KES. 

The  practical  point  in  these  Btudies  of  temperature  and  emergence 

relationships  is  to  ascertain  the  facts  upon  which  emergence  depends, 
so  that  it  may  he  possible  from  a  study  of  temperature  records  for  any 
locality  to  form  fairly  reliable  conclusions  as  to  the  effects  which  those 
temperature  conditions  may  have  had  upon  weevil  activity.  In  this 
way  it  may  be  possible  to  determine  approximately  the  time  when 
weevil  emergence  begins,  the  time  when  the  majority  of  weevils  will 
probably  have  left  their  hibernation  quarters,  and  approximately  the 
time  at  which  emergence  becomes  complete.  In  this  connection  it 
will  be  profitable  to  compare  the  records  for  Dallas,  Tex.,  with  those 
for  Keaxchle,  La.,  for  the  same  periods. 

The  total  effective  temperature  is  obtained  by  computing  the  sum 
of  the  mean  average  effective  temperatures  for  each  of  the  days 
included  within  the  period  shown.  For  example,  if  the  mean  average 
temperature  for  the  first  day  of  a  period  is  60°  and  for  the  second  day 
68°,  the  average  effective  temperature  for  the  two  days  is  17°  and  25°, 
respectively  .  The  sum  of  t  hese,  or  42°,  is  the  total  effect  ive  temper- 
ature for  those  two  dates. 


44  HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


Table  XX. — Relation  of  effective  temperatures  to  emergence  at  Keatchie,  La.,  and 

Dallas,  Tex.,  1906. 


Total  effective 

Average  effective 

Number  of  weevils 

temperature. 

temperature. 

emerging. 

Periods  of  emergence. 

Keatchie. 

Dallas. 

Keatchie. 

Dallas. 

Keatchie. 

Dallas. 

°F. 

°F. 

°F. 

°F. 

Mar.  15-21  

12.0 

5.5 

1.7 

0.78 

0 

0 

Mar.  22-27  

141.0 

151.8 

23.5 

25.3 

25 

2 

Mar.  28- Apr.  2  

37.0 

66.6 

7.4 

11.1 

12 

0 

Apr.  3-13  

275.5 

243.6 

25.0 

22.14 

165 

28 

Apr.  14-20  

118.5 

124.1 

16.9 

17.7 

28 

0 

Apr.  21-May  5  

484.7 

435.8 

32.3 

29.0 

187 

18 

May  6-13  

176.0 

159.8 

22.0 

19.9 

49 

0 

May  14-23  

339.0 

300.2 

33.9 

30.0 

173 

7 

May  24-29  

201.0 

196.8 

33.5 

32.8 

23 

0 

May  30- June  11  

413.0 

478.0 

37.5 

65 

June  12-30  

667.0 

700.0 

39.2 

7 

An  examination  of  this  table  shows  three  very  distinct  periods  of 
emergence,  the  first  being  from  April  3  to  13,  inclusive;  the  second 
from  April  21  to  May  5,  inclusive;  and  the  third  from  May  14  to  23. 
No  weevils  emerged  from  the  Dallas  cages  after  May  23.  At  Keatchie 
a  fourth  period  may  be  considered  as  occurring  between  May  30  and 
June  11.  In  this  place  the  emergence  ceased  on  June  28.  It  is 
noticeable  that  between  June  20  and  27  no  weevils  had  emerged. 
It  will  be  noticed  in  the  table  that  the  periods  of  largest  emergence 
are  separated  by  periods  having  decidedly  lower  temperatures, 
during  which  emergence  was  decreased,  although  it  did  not  cease 
entirely. 

The  relation  of  emergence  to  5-degree  increments  in  effective  tem- 
perature is  shown  in  Table  XXI. 

Table  XXI. —  The  relation  of  emergence  to  increase  in  effective  temperature  at  Keatchie, 

La.,  and  Dallas,  Tex.,  1906. 


Keatchie,  La. 

Dallas,  Tex. 

Range  of 

Total  num- 

Per cent, 

effective 

ber  of 

based  on 

tempera- 

Number of 

Per  cent  of 

Number  of 

Per  cent  of 

weevils 

grand  total 

tures. 

weevils 

total 

weevils 

total 

emerged. 

emerged. 

emerging. 

emergence. 

emerging. 

emergence. 

1-14°.... 

20 

2.7 

0 

0 

20 

2.5 

15-20°.... 

52 

7.1 

2 

3.6 

54 

6.8 

21-25°.... 

116 

16.0 

.25 

45. 5 

141 

17.8 

26-30°.... 

127 

17.5 

18 

32.7 

145 

18.5 

31-35°.... 

309 

42.4 

10 

18.2 

319 

40.7 

36-40°.... 

84 

11.5 

0 

0 

84 

10.7 

41-50°.... 

20 

2.7 

0 

0 

20 

2.5 

Total. 

728 

100.0 

55 

100.0 

783 

100.0 

The  number  of  weevils  emerging  under  14  degrees  of  effective 
temperature,  or  57°  F.,  is  very  small  indeed.  From  that  point  the 
emergence  increases  with  the  increase  in  temperature  until  after  a 
majority  of  the  weevils  have  emerged.  Most  weevils  left  their 
winter  quarters  during  an  effective  temperature  averaging  between 


LABGE-CAGE  EXPERIMENTS,  KEATCHIE,  LA.,  liH>5— <3. 


45 


21  and  35  degrees.  At  Keatchie  75  per  cenl  and  at  Dallas  96  percent 
of  the  total  emergence  took  place  between  these  limits.  At  Dallas 
the  largest  emergence  occurred  between  21  and  25  degrees  of  effective 
temperature,  while  at  Keatchie  the  largest  emergence  occurred 
between  :>1  and  oo  degrees. 

In  considering  the  effect  of  temperature  upon  emergence  it  must  be 
remembered  that  the  nature  of  the  shelter  within  which  the  weevil 
hibernates  must  inevitably  have  an  important  bearing  on  the  time  at 
which  the  weevil  becomes  active. 

RELATION   <)F  TIME  OF   ENTRANCE   into  HIBERNATION  TO  SURVIVAL 

AND  EMERGENCE. 

It  has  previously  been  stated  that  none  of  these  experiments  was 
instituted  more  than  about  ;i  week  before  it  became  cold  enough  for 
pract  ieally  all  weevils  to  hibernate.  For  this  comparison  it  is  pos- 
sible to  use  only  the  data  for  those  sections  having  similar  conditions 
as  to  (1)  the  source  from  which  weevils  were  obtained,  (2)  the  time 
when  they  were  placed  in  the  cage,  and  (3)  the  general  nature  of  the 
shelter  afforded. 


Table  XXII.— AV/a/io/i  of  lime  of  i  mi  rqrnn  in  I'joG  to  time  of  starting  hibernation 

in  1905. 


Section 

When  wee- 

iVn-entuLV of  total  rmiTtfenc*'.  !'.♦<>»'>,  occurring  in— 

Percent 

nuinlxT  in 
ca«e. 

vils  were 
put  in. 

March. 

April. 

May  1-14. 

May  15- 
June  L. 

June  2-30. 

of  sur- 
vival. 

Remarks. 

7  and  8  , 

14,  15,  and 
16. 

17  

Nov.  25 
and  29. 
Dec.  3  and 

3.7 
4.8 

46.3 
47.4 

28.7 
17.1 

15.7 
24.7 

5.5 
5.5 

3.0 
3.23 

jxexas  weevils. 

8. 

Nov.  28... 

9.7 

41.4 

28.3 

M  1 

22.0 

L\4 

4.  1 

j  Louisiana  weevils. 

18  

Nov.  18... 

0 

15.0 

32.0 

24.5 

5.3 

In  the  first  section  of  the  table,  among  weevils  collected  in  Texas, 
it  is  apparent  thai  there  was  practically  no  difference  in  the  time  of 
emergence  between  those  placed  in  hibernation  from  November  25 
to  29  and  those  started  December  'A  to  S.  Tn  the  second  part  of  the 
table,  among  the  Louisiana  weevils,  those  entering  hibernation 
November  18  emerged  more  slowly  than  did  those  placed  in  the  cage 
November  28.  The  explanation  of  this  may  probably  be  found  in 
the  fact  that  the  first  date  was  not  sufficiently  early  to  insure  the 
death  of  many  weevils  by  starvation  before  they  could  hibernate. 
It  did,  however,  allow  a  larger  proportion  of  them  to  penetrate  deeply 
into  the  shelter  than  in  the  case  of  weevils  placed  in  the  cage  ten  days 
later,  which  was  only  one  day  before  a  marked  decrease  in  tempera- 
ture. The  weevils  placed  in  the  cage  on  December  3  and  8  experi- 
enced warmer  temperatures  than  those  placed  in  on  the  28th  of 
November,  and,  therefore,  found  conditions  more  favorable  for  their 


46 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


entrance  into  hibernation.  The  records  indicate  that  there  is  a  most 
favorable  time  for  entrance  during  which  weevils  may  find  shelter 
from  which  they  will  emerge  rather  later  than  the  average  during  the 
following  spring. 

THE  RELATIONSHIP   OF   ACCUMULATED   EFFECTIVE   TEMPERATURE  TO 

EMERGENCE. 

In  studying  the  relationship  of  accumulated  effective  temperature 
to  emergence  the  initial  point  has  been  set  arbitrarily  at  February  1. 
It  would  be  both  interesting  and  profitable  if  we  could  determine 
positively  the  exact  effective  temperature  conditions  under  which 
emergence  from  hibernation  begins.  This  point  will  be  further  dis- 
cussed in  the  light  of  the  additional  records  obtained  in  Texas  in  1907. 

The  object  in  this  particular  study  is  to  determine  the  relation 
of  accumulated  effective  temperature  to  the  accumulation  in  emer- 
gence. The  records  for  both  Keatchie  and  Dallas  are  included  for  the 
sake  of  comparison. 


Table  XXIII. — Relation  of  accumulated  effective  temperature  to  the  beginning  and 
accumulation  of  emergence,  Keatchie,  La.,  and  Dallas,  Tex. 


Periods  of  emergence. 

Accumulated  ef- 
fective tempera- 
ture. 

Accumulated  num- 
ber   of  weevils 
emerged. 

Accumulated  per- 
centage of  total 
emergence. 

Keatchie. 

Dallas. 

Keatchie. 

Dallas. 

Keatchie. 

Dallas. 

1906. 

°F. 

°F. 

Feb.  28  :  

145.6 

208.  6 

0 

0 

0 

0 

Mar.  1-14  

282. 1 

325.  0 

0 

0 

0 

0 

Mar.  15-21  

294.1 

330.5 

0 

0 

0 

0 

Mar.  22-27  

435.1 

482.3 

25 

2 

3.4 

3.6 

Mar.  28-Apr.  2  

472.1 

548.9 

37 

2 

5.0 

3.6 

Apr.  3-13  

747.6 

792.5 

202 

30 

27.5 

54.5 

Apr.  14-20  

866.1 

916.6 

230 

30 

31.3 

54.5 

Apr.  21-May  5  

1,350.8 

1,362.4 

417 

48 

56.8 

87.2 

Mav  6-13  

1,526.8 

1.512.2 

466 

48 

63.4 

87.2 

May  14-23  

1,865.8 

1,812.4 

639 

55 

87.0 

100.0 

May  24-29  

2,066.8 

2,009.2 

662 

55 

90.0 

Mav  30-June  11  

2,479.8 
3,146.8 

2,487.6 
3,188.0 

727 
734 

55 
55 

99.0 
100.0 

June  12-30  

Emergence  at  Dallas  became  complete  with  the  accumulation  of 
slightly  over  1,800  degrees  of  effective  temperature,  while  at  Keatchie 
complete  emergence  required  slightly  over  3,000  degrees  of  effect- 
ive temperature.  At  Dallas  87  per  cent  of  weevils  had  emerged 
when  1,512  degrees  of  effective  temperature  had  accumulated  and 
the  same  percentage  had  emerged  at  Keatchie  with  1,865  degrees 
effective  temperature.  For  the  last  13  per  cent  of  weevils  emerging 
but  300  degrees  of  temperature  accumulated  at  Dallas,  while  at 
Keatchie  nearly  1,300  degrees  accumulated.  It  is  probable  (hat  al 
Dallas  during  this  season  the  emergence  in  the  cage  was  completed 
somewhat  sooner  than  would  have  been  the  case  normally,  on  account 
of  the  late  period  of  starting  the  experiments. 


LAUGH-CAGE  EXPERIMENTS.  KEATCHIE,  LA. ,  1905-6. 


47 


At  Victoria  in  the  spring  of  1904  the  period  of  emergence  from 
hibernation  was  determined  in  the  field  under  exceptionally  favor- 
able conditions.  A  severe  drought,  occurring  immediately  after 
most  of  the  cotton  had  been  planted,  so  retarded  germination  that 
the  sprout  cotton  developed  nearly  two  months  in  advance  of 
the  planted.  Large  numbers  of  weevils  emerged  before  most  of  the 
planted  cotton  was  through  the  ground.  Practically  the  only  food 
supply  afforded  these  weevils  was  found  in  the  sprout  cotton.  By 
reducing  the  number  of  sprout  plants  upon  a  field  of  65  acres  it  was 
possible  to  examine  at  frequent  intervals  all  of  the  plants.  Since 
all  weevils  found  at  each  examination  were  collected  and  removed 
from  the  field  those  found  at  the  next  subsequent  examination  may 
be  considered  as  having  emerged  in  the  interval.  The  development 
of  squares  upon  the  most  advanced  plants  was  not  sufficient  to 
make  it  possible  for  any  weevils  of  the  first  generation  to  have  become 
adults  before  June  1.  The  collections  from  the  sprout  plants  were 
continued  until  May  26,  and  it  is  probable  that  some  weevils  emerged 
from  hibernation  after  this  date.  ( )ur  know  ledge  of  the  weevils  at  that 
time  was  not  such  as  to  enable  us  to  distinguish  accurately  between 

hibernated  and  recently  emerged  adults  after  that  date.  For  that 
reason  May  26  was  considered  as  representing  the  conclusion  of 
emergence  from  hibernation,  although  it  probably  continued  longer. 

Tablk  XXIV.    Relation  of accumulated  cffcctin  t>  m  p,  ratun  to  accumulated  emergent* 
in  field  obsi  n  ations  at  Yictoriu.  Tex.t  in  1904, 


I'erlods. 


Feb.  1-28.... 
Mar.  I  is... 
Mar.  19-25.. 
Mar.  M 

Apr.  1-5  

Apr.  6  12.  . 
Apr.  13  16. 
Apr.  17-Mav 
Mav  2  11.... 
Mi'.  12  I1'... 
Mav  20-20.  .  . 


Accumu- 
late. 1 
effective 
temj>era- 
ture. 


F. 

50S.0 

.117.5 
,240.  0 
.M7v:> 
..V17.  il 

!,.-.<,.  II 

.104.0 

,374.0 
.5S4.0 
.M4.5 


Accumu- 
lated 

Dumber 

of  plants 
of  cotton 
sprouts 
examined. 


None. 
250 
650 
1,190 
1,720 
2,120 
2,320 
2.570 
2,990 
4,163 
.->.ooo 


Accumu- 
lated 
percentage 

of  plant- 
examined 

to  entire 

numbs 

examined. 


None. 
4.2 
11.0 
20.1 
29.1 
35.9 
39.3 
43.5 
50.6 
70.5 

100.0 


Accumu- 
lated 
Dumber  of 

weevils 
found. 


None. 
19 
39 
65 
100 
100 
200 
224 
376 
521 
64N 


Accumu- 
lated 
percentage, 
of  weevils 
at  each  date 
to  entire 
numl»er 
found. 


None 
2.93 
6.01 
10. 0o 
15.  40 
24. 60 
30.L«iC 
34.  50 
5S.0C 

si.  or 

100.  00 


A  comparison  of  Tables  XXIII  and  XXIV  shows  that  there  was  a 
much  greater  accumulation  of  temperature  at  Victoria  for  the  same 
percentage  of  emergence  than  occurred  at  either  Dallas  or  Keatchie, 
although  the  Keatchie  record  appeals  to  exceed  the  Victoria  record 
in  the  amount  of  accumulated  temperature  accompanying  complete 
emergence.  It  seems  very  probable  that  in  the  field  records  the 
accumulations  are  excessive  because  of  two  facts;  first,  at  each 


48 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


examination'  all  weevils  were  considered  as  emerging  upon  the  date 
of  the  examination,  whereas  in  the  cages  the  weevils  were  collected 
daily.  The  second  reason  is  that  upon  plants  in  the  field  there  was 
a  much  greater  possibility  of  overlooking  weevils  which  were  present 
and  which  might  be  found  and  counted  as  having  emerged  upon 
some  succeeding  examinations.  Table  XXIV  is,  however,  of  value 
in  supporting  the  records  given  in  Table  XXIII,  especially  because 
similarly  favorable  conditions  for  determining  the  full  period  of 
emergence  in  the  field  may  rarely  occur. 

LONGEVITY    OF    WEEVILS   AFTER    EMERGENCE    IN    KEATCHIE  EXPERI- 
MENTS. 

For  determining  longevity  after  emergence  the  weevils  emerging 
during  short  periods  were  placed  together  in  a  smaller  cage  provided 
with  a  variety  of  rubbish  but  with  no  food.  Examinations  of  the 
small  cages  were  made  at  frequent  intervals  and  the  period  between 
the  average  date  when  weevils  were  placed  in  the  cage  and  the  aver- 
age date  of  examinations  was  recorded.  The  figures  are  arranged 
chronologically  according  to  emergence. 

Table  XXV. — Longevity  of  weevils  after  emergence  from  hibernation,  without  food,  at 

Keatchie,  La.,  1906. 


Date  of  emergence. 


1906. 
March  26. . . . 

April  10  

April  11  

April  12  

April  13  

April  14  

April  15  

April  16  

April  17  

April  19  

April  20  

April  21.... 
April  22.... 

April  23  

April  24.... 
April  25.... 
April  26.... 
April  28.... 
April  30.... 

May  1  

May  2  

May  4  

May  5  


Number 
of  weevils 
emerged. 


Weevil 
days.a 


62.0 
905  .5 
751.  0 
678.5 
261.  0 
169.0 
100.5 

59.0 


55.0 
119.0 
92.0 
378.5 
132.5 
36.0 
83.5 
24.0 
855.  0 
313.0 
15.0 
173.  0 
431.0 
342.  0 


Average 
number 
of  days 
lived. 


62.0 
21.7 
21.4 
23.4 
32.6 
24.1 
20.1 
29.5 


27.5 
10.8 
10.2 
16.4 
22.0 
9.0 
9.2 
8.0 
18.5 
17.3 
7.  5 
11.5 
15.3 
18.0 


Date  of  emergence. 


1906. 

May  7  

May  8  

May  10  

Mav  11  

May  12  

May  13  

May  14  

May  15  

May  16  

May  17  

May  18  

May  22  

May  23  

May  25  

May  28  

May  29  

May  30  

Juiie  9  

June  19  

Totals  and 
average . . . 


Number 
ofweevils 
emerged . 

Weevil- 
days.* 

Average 
number 
of  days 
lived. 

16 

292.5 

18.2 

16 

262.0 

16.3 

1 

1.0 

1.0 

6 

54.5 

9.0 

5 

13.0 

3.2 

1 

1.5 

1.5 

8 

58.5 

7.3 

2 

26.0 

13.0 

13 

169.5 

13.0 

6 

58.0 

9.6 

4 

48.5 

12.1 

2 

23.5 

11.7 

2 

29.0 

14.5 

2 

26.5 

13.2 

1 

1.5 

1.5 

1 

7.5 

7.5 

4 

35.0 

8.7 

1 

7.0 

7.0 

1 

4.0 

4.0 

418 

7, 155. 0 

17.11 

«In  the  third  column  of  the  table  the  expression  "weevil-days"  is  used  to  signify  the  total  number  of 
days  lived  by  the  total  number  of  weevils  recorded  for  a  certain  date.  For  example,  if  one  weevil  had 
lived  10  days,  a  second  15  days,  and  a  third  23  days  the  total  number  of  weevil-days  for  these  3  individuals 
would  be  48  and  the  average  number  of  days  lived  would  be  16. 

It  is  not  iceable  that  weevils  emerging  early  in  t  he  season  survived 
far  longer  than  the  average  period,  while  those  emerging  toward  the 
end  of  the  season  survived  for  less  than  the  average  period.  For 
the  lis  weevils  tested  the  average  duration  of  life  without  food 
proved  to  be  slightly  over  seventeen  days. 


LARGE-CAGE  EXPERIMENTS  AT  DALLAS,  TEX.,  1905-6.  49 


LARGE-CAGE  EXPERIMENTS  AT  DALLAS,  TEX.,  1905-6. 


The  work  at  Dallas  for  1905-6  was  planned  especially  to  check 
the  results  of  the  experiments  at  Keatchie  which  have  been  described. 
The  cage  used  (PI.  IV,  fig.  1)  was  divided  into  four  sections,  each 
having  a  ground  area  of  100  square  feet.  In  one  section  the  natural 
conditions  of  shelter  were  left  unchanged  (PI.  IV,  fig.  2).  There 
was  practically  no  grass  upon  the  ground,  but  the  growth  of  stalks 
was  quite  heavy.  In  the  other  three  sections  the  shelter  provided 
(PL  V,  figs.  1  and  2)  for  the  weevils  was  arranged  in  such  a  way 
that  it  might  be  possible  to  divide  each  section  into  two  parts  by  a 
middle  partition.  Unfortunately  the  first  cold  weather  occurred 
before  the  weevils  could  be  placed  in  these  sections,  and  it  was  neces- 
sary to  keep  the  weevils  confined  in  boxes  for  several  days  until  it 
became  sufliciently  warm  to  render  them  active  so  that  they  might 
filld  shelter  in  the  cages.  The  weevils  were  liberated  at  approxi- 
mately the  center  of  each  .section  and  allowed  to  move  in  any  direc- 
tion they  might  choose.  The  object  of  this  was  to  determine  whether 
particularly  favorable  rubbish  might  exert  a  special  attraction  for 
the  weevils. 

About  three  weeks  after  the  weevils  were  liberated  an  examina- 
tion was  made  of  each  section  and  the  number  of  weevils  crawling 
actively  upon  the  wire  was  determined.  An  examination  of  the 
boxes  from  which  the  weevils  were  liberated  and  which  had  been 
left  undisturbed  in  the  cages  during  this  period  showed  that  a  large 
mortality  had  occurred  before  the  weevils  really  entered  hibernation. 
Table  XXVI  shows  the  principal  points  in  regard  to  the  beginning 
of  the"  experiments  and  the  emergence  of  the  weevils  during  the 
following  spring. 

TABU  XXVI.-   Laryt-cayt  tip<rinunts  in  hibernation  at  Dallas,  TtX.t  1905-6. 


Section 
of  cage. 

Kind  of  shelter. 

Weevils 
put  in. 

Active 
weevils, 

1  >IVt'III- 

l>er  20, 
1905. 

Weevils 
found 
(lead. 

Decem- 
ber 26, 

1905. 

Percent- 
age of 
\vee\  ils 
active, 

i  )we  rn- 
tar,  1905. 

Percent- 
age of 
living 
among 
those  ex- 
amined. 

I  

II: 

Pi  l... 

Pt  2... 

Ill: 

rt.  i  . . . 

Pt.  2... 

IV: 

rt. 

Pt.  2... 

Cotton  stalks  

Cotton  stalks  re- 
in oved  March 
22.  1906. 

Cotton  stalks  and 
leaves. 

Bare  

Hay  

2,000 
2,500 

375 
200 

015 
515 

14.4 

8.0 

3N.0 
2S.0 

2,500 

2(i0 

1,205 

10.4 

17.7 

Piled  boxes  

Corn  and  cotton 
stalks. 

Total  and 
average. 

2,500 

238 

1,025 

9.5 

12.7 



10,100 

1,073 

3,9ti0 

10.0 

21* 

Date  of 
first 
emer- 
gence, 

1900. 

Day  of 
largest 
emer- 
gence, 
1900. 

Apr.  4 

May  2 

Mar.  22 

Apr.  9 

Apr.  4 

Apr.  11 

Apr.  23 
May  It 

Apr.  23 
May  14 

Apr.  4 
Apr.  9 

Apr.  11 
Apr.  9 

00317— Bull.  77—09  1 


50  HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 

Table  XXVI. — Large-cage  experiments  in  hibernation  at  Dallas,  Tex.,  1905-6 — Con. 


Kind  of  shelter. 


Cotton  stalks  

Cotton    stalks  removed 

March  22,  1906. 
Cotton  stalks  and  leaves. . 

Bare  

Hay  

Piled  boxes  

Corn  and  cotton  stalks  

Total  and  average. . 


Emergence  by  periods. 


Mar. 
22-31. 


Apr. 
1-10. 


Apr. 
11-20. 


Apr. 
21-30. 


May 
1-10. 


May 
11-20. 


Total 
sur- 
vival. 


21-31. 

0 

0 

0 

0 
0 

2 
0 


12 


18 


56 


The  division  of  sections  2,  3,  and  4  was  made  by  inserting  a  par- 
tition of  cheese  cloth  early  in  the  spring  of  1906  before  any  weevils 
became  active.  The  percentage  of  survival  has  been  based  upon 
the  total  number  of  weevils  placed  in  the  four  sections.  It  should 
be  borne  in  mind  that  the  conditions  at  the  time  of  entrance  into 
hibernation  were  decidedly  unfavorable  for  the  weevils,  as  is  shown 
in  the  fact  that  about  35  per  cent  had  died  before  December  26  and 
under  such  conditions  as  to  indicate  that  they  were  very  weak  at  the 
time  they  were  placed  in  the  cage.  No  allowance  has  been  made  for 
the  escape  of  weevils  through  the  wire.  It  thus  appears  that  approxi- 
mately 1  per  cent  of  the  weevils  which  really  may  be  said  to  have 
entered  hibernation  survived  and  emerged  between  March  21  and 
May  31.  The  survival  in  the  bare  section  was  less  than  one-fourth 
of  the  smallest  survival  in  the  sections  provided  with  rubbish.  For 
the  sake  of  comparison  with  the  records  at  Keatchie,  La.,  some  data 
from  the  Dallas  experiments  have  been  used  in  connection  with 
those  at  Keatchie  in  several  of  the  tables  which  have  already  been 
given. 

NATURE  OF  WEEVIL  ACTIVITY  FOLLOWING  EMERGENCE  FROM  HIBER- 
NATION. 

In  following  the  activity  of  emerged  weevils  it  was  deemed  advis- 
able to  pursue  a  very  different  method  at  Dallas  from  that  which 
has  been  described  at  Keatchie.  Instead  of  removing  weevils  from 
the  sections  in  which  they  had  emerged,  each  weevil  was  marked  in 
such  a  way  as  to  make  it  possible  to  recognize  it  individually  and  the 
weevils  were  allowed  to  remain  practically  undisturbed  in  the  sec- 
tion where  they  had  spent  the  winter.  In  making  the  daily  exam- 
inations record  was  kept  of  the  appearance  or  disappearance  of  each 
individual  weevil.     \'o  food  was  supplied  in  any  of  the  sections  until 


Bui  77  Bureau  of  Entomology,  U.  S  Dept.  of  Agriculture. 


Plate  IV. 


Hibernation  Experiments,  Dallas,  Tex.,  1905-6. 

Fig.  1.— Four-section  cage  used  for  experiments,  built  over  cotton.   Fig.  2. — Shelter  conditions  as 
occurring  naturally  in  section  1.  (Original.) 


Bui.  77,  Bureau  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


Plate  V. 


Shelter  Conditions  in  Dallas,  Tex.,  Experiments.  1905-6. 

Fig.  1. — Piled  cotton  stalks  and  piled  boxes  in  section  2.    Fig.  2. — Standing  cotton  stalks  versus 
piled  leaves,  section  3.  (Original.) 


LABOE-CAOB  EXPERIMENTS  AT  DALLAS,  TEX.,  11)05-6. 


51 


toward  the  close  of  the  experiments  in  May,  when  seed  was  planted 
and  cotton  began  growing  before  the  last  weevils  emerged.  Some 
very  interesting  results  were  obtained  from  this  method  of  observa- 
tion. A  majority  of  the  weevils  were  seen  a  second  time,  and  some 
disappeared  and  reappeared  as  many  as  eight  times.  The  longest 
period  between  the  first  and  second  appearances  of  any  individual 
was  forty-three  days. 

Tahi.k  XXVII.  -Intt  rmitti  >d  drtn  itii  of  v  nftd  v -< < ■  n'/ '.s  after  <  mergence ,  at  Dallas,  YV.r., 

1906. 


Weevils  "rehibernated"- 

i 

Numlxr  of  weevils  seen— 

B 

Once. 

Twii-e. 

Three  times. 

i 

B 
O 

i 

Tliree  times. 

1 

5 

±_ 

Five  times. 

i 
| 

M 

Seven  times. 

1 
I 

H 

NuiiiImt. 

•s. 

\ 

Q 

I 
I 

Q 

i 
i 

1 

Q 

=  o 

i! 
s 

-< 

46 

26 

15 

11 

6 

2 

2 

17 

8.7 

6 

7.2 

2 

3.5 

6.8 

As  lias  been  previously  shown,  entrance  into  hibernation  is  a 
gradual  process  and  weevils  which  have  fust  become  quiet  may  sub- 
sequently become  active  and  seek  other  shelter  before  finally  hiber- 
nating. In  a  very  similar  way  emergence  from  hibernation  is 
gradual  but  extended  throughout  a  longer  period  of  time  than  is 
entrance  into  hibernation.  The  observations  recorded  in  Table 
XXVII  also  show  conclusively  that  weevils  may  leave  their  winter 
quarters  during  warm  days  and.  failing  to  find  food,  they  may  again 
become  quiet  and  emerge  again  after  a  considerable  interval.  This 
fact  has  an  important  bearing  upon  the  proposition  which  is  fre- 
quently advanced  by  planters  of  starving  the  weevils  in  the  spring 
by  deferring  the  time  of  planting.  While  many  weevils  might  perish 
in  this  way,  it  is  certain  that  many  more  would  be  able  to  survive 
and  reappear  at  intervals,  so  that  there  would  be  plenty  of  weevils 
to  infest  tne  crop,  even  though  this  might  be  planted  as  late  as  is 
possible  to  secure  any  yield. 

Other  observations  were  made  upon  the  intermittent  activity  of 
unfed  weevils  during  the  spring  of  1906.  Weevils  from  Calvert, 
Victoria,  and  Brenham,  Tex.,  were  tested.  The  weevils  From  Cal- 
vert and  Victoria,  Tex.,  had  been  confined  in  hibernation  cages 
throughout  the  winter.  Those  from  Brenham  were  collected  in  the 
held  early  in  March.  None  of  these  weevils  had  tasted  food  after 
emergence.  In  these  tables  the  date  of  death,  unless  otherwise  indi- 
cated, is  considered  as  having  been  the  middle  date  between  the  last 
examination  at  which  a  weevil  was  found  alive  and  that  at  which  it 
was  found  dead. 


52  HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 

Table  XXVIII. — Intermittent  activity  of  unfed  emerged  weevils,  1906. 


Locality. 

When 
collected. 

When 
put  in  hi- 
bernation. 

When 
removed 
from  hi- 
bernation. 

When 
rehiber- 
nated. 

Weevils 
put  in  rehi- 
bernation. 

Date  of 
first  ex- 
amina- 
tion. 

Calvert,  Tex  

1905 
Nov.  25 
/Nov.  7,13 
\Dec.  11 

1906 
Nov.  1 

1905 
Nov.  27 
Nov.  7,13 
Dec.  11 

1906 
Apr.  19 

j-Apr.  6 
Mar.  1 

1906 
Apr.  23 

Apr.  16 
Mar.  7 

20 
7 

8 

May  10 
Apr.  24 

May  11 

Victoria,  Tex  

Brenham,  Tex  

Locality. 

Weevils 
surviv- 
ing. 

Date  of 
second 
exami- 
nation. 

Weevils 
surviv- 
ing. 

Date  of 
third 
exami- 
nation. 

Weevils 
surviv- 
ing. 

Date  of 
death  of 
longest 
survival. 

Average 
length  of 
life  in 
rehiber- 
nation. 

Calvert,  Tex  

Victoria,  Tex  

10 
3 
2 

May  22 
May  10 
May  23 

6 
0 
1 

June  8 

0 

June  8 
May  10 
May  31 

Days. 
30.4 
19.1 
67.4 

Brenham,  Tex  

May  31 

0 

The  records  for  Calvert  and  Brenham  show  a  very  remarkable 
power  of  endurance  in  some  weevils,  the  average  survival  for  the 
two  lots  of  20  and  8  weevils  being  over  thirty  and  sixty  days, 
respectively. 

CLIMATIC    CONDITIONS    PRODUCING    EMERGENCE    FROM  HIBERNATION 
AT  DALLAS,  TEX.,  IN  1906. 

In  the  figure  given  below,  representing  climatic  conditions  and 
the  emergence  at  various  dates,  the  temperature  line  given  repre- 
sents only  the  mean  average  effective  temperature. 

In  this  case,  as  at  Keatchie,  the  emergence  occurred  especially  dur- 
ing four  well-defined  periods  and  the  conclusions  stated  in  connection 
with  figure  1  apply  equally  well  to  the  results  shown  in  figure  2. 

EMERGENCE  IN  THE  FIELD  AT  VICTORIA,  TEX.,  IN  1906. 

The  observations  upon  emergence  in  the  field  at  Victoria,  Tex., 
in  1906,  were  begun  too  late  in  the  spring  to  indicate  the  limits  of 
the  first  part  of  the  period  of  emergence.  For  this  work  a  field  of 
about  one-half  acre  was  selected  in  which  it  was  apparent  early  in 
May  that  there  would  be  a  large  number  of  hibernated  adults.  The 
observations  were  planned  to  furnisli  information  particularly  upon 
two  points  under  field  conditions:  (1)  The  determination  of  the 
period  of  emergence  and  (2)  the  period  of  activity  of  emerged  wee- 
vils. The  work  was  done  by  Mr.  A.  C.  Morgan,  who  devoted  par- 
tienlnr  attention  to  a  study  of  this  field  throughout  the  season  of 
L906.  The  method  followed  was  to  examine  every  plant  and  every 
square  or  boll  throughout  this  area.    After  the  first  two  examina- 


EMERGENCE  IN  THE  FIELD  AT  VICTORIA,  TEX., 'IN  100f>. 


53 


tions  had  been  made  it  became  apparent  that  some  method  must  be 
adopted  to  enable  the  weevils  found  at  each  examination  to  be  dis- 
tinguished. At  each  subsequent  examination,  therefore,  the  wee- 
vils found  were  marked  with  a  paint  of  a  different  color.  Early  in 
the  season  the  weevils  emerging  from  hibernation  were  sufficiently 
numerous  to  practically  prevent  the  setting  of  fruit  upon  this  area. 
The  first  weevils  of  a  new  generation  did  not  begin  to  appear  until 


3.50 

350 
3  oo^ 
250$ 





2  00$ 
| 

t  oo  J 
050 

KI.RO 
£1.00 
0.50 

c 



J 

= 

t 

L 

1 

r. 

t 

[/II 

ii 

0 

Fig.  2.— Chart  showing  moan  average  temperature,  rainfall,  and  weevil  emergence,  Dallas,  Tex.,  March 

to  May.  1906. 

about  June  20.  It  was  then  easily  possible  to  distinguish  between 
hibernated  adults  and  those  which  were  not  more  than  two  or  three 
weeks  old.  It  is  probable  that  the  oil  paints  which  were  used  may 
have  been  responsible  for  the  death  of  many  of  the  weevils  marked, 
since  it  was  hardly  possible  in  the  field  to  apply  the  paints  with  the 
necessary  care. 


54  HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


Table  XXIX. — Emergence  records  for  one-half -acre  field  at  Victoria,  Tex.,  1906. 


Date  of  examina- 
tion. 

Number  of  weevils  found. 

Remarks. 

Unmarked. 

Marked 
yellow. 

Marked 
blue. 

Marked 
red. 

Total  num- 
ber found. 

1906. 

May  19  

346 
358 

492 
226 
165 
731 

c? 

? 

? 

? 

346 

358 

492 

355 
228 
739 

Weevils  not  removed. 
Do. 

Weevils  marked  yellow=492. 
Weevils  marked  blue=226. 
Weevils  marked  red=87. 
Weevils  marked  white=78. 

May  25  

May  28.a 

June  3-5  

June  13  

129 
27 
3 

June  23-July  5 

9 
0 

18 
0 

9 
1 

July  23-26  

Total  

2 

2 

2,318 

159 

9 

18 

10 

2 

2  2,518 

o  Eighty-seven  weevils  removed  from  field  May  28  for  other  experimental  work. 


It  is  evident  from  an  examination  of  the  number  of  weevils  found 
that  the  number  in  the  field  increased  steadily  until  after  June  5. 
Between  June  5  and  13  a  large  number  of  previously  marked  weevils 
appeared,  all  of  which  were  undoubtedly  hibernated.  The  very 
small  number  of  first-generation  weevils  which  was  found  upon  the 
examination  made  between  June  23  and  July  25  was  due  primarily 
to  the  exceptionally  severe  hot  dry  weather  which  had  prevailed  for 
several  weeks.  The  gradual  decrease  in  the  number  of  living  hiber- 
nated weevils  was  greater  than  the  increase  in  the  number  of  first- 
generation  weevils.  During  the  period  between  the  middle  of  June 
and  the  middle  of  July  the  plants  rapidly  increased  their  fruiting 
activity  and  there  was  a  decided  decrease  in  weevil  injury.  It  is 
interesting  to  note  that  in  spite  of  the  large  number  of  hibernated 
weevils  occurring  in  this  field,  which  threatened  early  in  the  season 
to  prevent  entirely  the  setting  of  fruit,  the  weevil  injury  and  devel- 
opment were  so  checked  by  the  heat  and  drought  that  after  the 
middle  of  July  these  plants  set  fruit  rapidly  and  the  field  produced 
an  average  yield  of  cotton. 

The  most  plausible  explanation  of  the  late  period  of  emergence  for 
weevils  found  in  this  field  is  the  existence  in  its  immediate  vicinity 
of  a  large  number  of  trees  which  were  loaded  with  long  Spanish  moss. 
(See  PI.  II,  figs.  1,2.)  The  explanation  of  the  effect  of  this  moss  in 
producing  late  emergence  from  hibernation  will  be  considered  more 
particularly  in  connection  with  the  cage  experiments  in  hibernation 
for  L906  to  1907. 


LARGE-CAGE  EXP  E  R IMENTS,  1906—7. 


55 


LARGE-CAGE  EXPERIMENTS,  DALLAS,  CALVERT,  AND  VICTORIA, 

TEX.,  1906  7. 

PLAN  OF  EXPERIMENTS. 

Profiting  by  the  work  done  during  former  seasons,  plans  wore  made 
by  Mr.  W.  D.  Hunter,  in  charge  of  the  investigations,  for  much  more 
careful  and  extensive  work  during  the  winter  of  190G-7  than  had 
ever  been  undertaken.  Three  localities  for  the  experimental  work 
were  selected  representing  in  a  general  way  the  northern,  central,  and 
southern  sections  of  the  State.  In  these  localities,  also,  much  work 
had  previously  been  done  and  the  results  for  more  than  one  season 
could  therefore  be  used  in  a  comparative  way.  At  Dallas,  Calvert, 
and  Victoria  screen-covered  cages  were  erected,  each  being  20  feet 
wide,.")!)  feet  long. and  about  (P.  feet  high.  (PI.  VI,  figs.  1,  2,  and  3.) 
These  cages  were  divided  into  ten  sections  by  partitions,  each  section 
having  a  ground  area  of  1 00  square  feet .  The  t  hree  localities  selected 
offered  a  considerable  range  in  geographical  and  climatic  conditions. 

Each  section  of  the  cage  was  provided  with  a  door  opening  to  tin4 
outside  through  which  access  could  be  had  to  a  section  without 
disturbing  the  conditions  in  any  other  section.  It  was  planned  to 
provide  similar  conditions  of  shelter  in  corresponding  sections  and 
to  confine  weevils  in  corresponding  sections  at  as  nearly  the  same 
date  as  might  be  possible  in  each  of  the  three  sections;  The  weevils 
used  were  collected  in  the  immediate  locality  where  they  were  placed 
in  hibernation.  In  this  way  it  was  anticipated  that  data  might  be 
obtained  bearing  especially  upon  the  following  points: 

(1)  The  effect  of  the  time  of  entrance  into  hibernation  upon  the 
survival  of  weevils.  In  the  experiments  first  started  it  was  necessary 
to  force  entrance  into  hibernation,  if  possible,  or  starvation  by  the 
destruction  of  the  food  supply.  The  geographical  range  was  expected 
to  increase  the  interval  between  the  beginning  of  the  experiment  in 
each  locality  and  the  time  when  weevils  would  normally  hibernate. 

(2)  The  effect  which  the  complete  destruction  of  food  supply  at 
varying  dates  might  have  upon  the  success  of  hibernation.  For  these 
experiments  the  shelter  conditions  were  as  uniform  and  as  favorable 
as  it  was  possible  to  make  them  in  the  different  localities.  It  was 
hoped  through  these  tests  to  determine  the  minimum  interval  which 
must  elapse  between  the  destruction  of  stalks  and  the  successful 
hibernation  of  the  weevils. 

(3)  To  determine  the  effect  of  exceptionalh'  favorable  and  unfavor- 
able conditions  of  shelter  upon  the  hibernation  of  weevils  placed  in 
the  cages  upon  the  same  date.  It  was  intended  that  the  shelter 
conditions  provided  should  be  so  exaggerated  as  to  represent  the 
extremes  of  conditions  which  might  naturally  occur  in  the  field. 


5G 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


(4)  To  determine  the  effect  which  different  depths  and  classes  of 
shelter  might  exert  upon  the  success  of  hibernation  and  also  upon  the 
time  of  emergence  and  the  range  of  the  emergence  period. 

(5)  To  test  the  power  of  adaptation  which  the  weevils  might  have 
acquired  to  varying  climatic  conditions  by  bringing  weevils  from 
widely  separated  localities  for  comparison  with  weevils  collected  at 
Dallas.  In  each  test  similar  conditions  of  food  and  shelter  should 
exist  in  each  locality. 

(6)  To  determine  upon  a  large  scale,  in  very  widely  separated 
localities,  the  proportion  of  weevils  entering  hibernation  which  might 
survive. 

(7)  To  determine  the  relation  between  climatic  conditions  and  the 
emergence  period  in  each  locality.  To  provide  suitable  and  reliable 
data  for  this  study,  standard  Weather  Bureau  instruments  were 
secured  and  temperature,  humidity,  rainfall,  and  other  records  were 
kept  in  each  locality  throughout  the  period  covered  by  the  experi- 
ments. 

(8)  To  determine  the  longevity  of  hibernated  weevils,  especially 
after  emergence.  Since  all  weevils  used  in  this  work  were  collected 
promiscuously  in  the  field  immediately  preceding  their  confinement 
in  the  cages,  all  figures  showing  their  longevity  must  be  based  either 
upon  the  date  when  they  were  placed  in  hibernation  or  upon  the  date 
of  their  emergence.  In  the  latter  case  it  would  be  distinguished  as 
longevity  after  emergence. 

It  was  planned  to  use  from  2,500  to  3,000  weevils  in  each  section 
of  the  cages,  although  difficulties  in  the  collection  of  the  desired 
number  for  the  particular  dates  when  experiments  were  to  be  started 
occasionally  caused  some  variation  in  this  number.  Adult  weevils 
only  were  used  in  sections  1  to  9,  inclusive,  in  each  cage,  while  in  sec- 
tion 10  the  hibernation  of  weevils  in  bolls  was  tested.  One-half  of 
the  bolls  were  buried  under  2  inches  of  dirt.  The  other  half  were 
exposed  upon  the  surface  of  the  ground.    (PI.  X,  fig.  1.) 

It  is  generally  understood  that  the  principal  factor  producing  a 
hibernation  period  is  the  lower  temperature  occurring  during  the  fall 
and  winter  months.  In  its  effect  upon  the  survival  during  this  period 
moisture  is  also  an  important  factor.  As  a  rule,  in  studies  of  these 
factors  investigators  have  been  obliged  to  rely  upon  the  climatic 
reports  published  by  the  United  States  Weather  Bureau  for  the  par- 
ticular locations  desired.  It  happens  frequently,  however,  that 
there  may  be  no  report  from  the  Weather  Bureau  for  the  particular 
locality  desired.  Both  temperature  and  rainfall  are  liable  to  con- 
siderable variation  within  comparatively  short  distances.  In  order 
thai  the  data  for  these  studies  of  the  hibernation  of  the  boll  weevil 
might  be  complete  and  thoroughly  reliable,  we  have  kept  full  climatic 
records  in  the  immediate  vicinity  where  experiments  and  cage  obser- 


Bui.  77,  Bureau  o<  Entomology,  U  S  Dept.  of  Agriculture 


Plate  VI. 


JJJ 


mam 


Cages  for  Hibernation  Experiments  in  Texas,  1906-7. 


Fig.  1.— Dallas,  Tex.,  cage  on  flat,  black- 


is.  i.-i^t...^,  xv.v.,  tQ5C  uu  uai,  ukh  »-wiixv  land.  Fig.  2. — Calvert,  Tex.,  cage  on  slightly 
sloping,  sandy  land  in  post-oak  region.  Fig.  3.— Victoria,  Tex.,  cage  on  sandy-loam  slope 
between  bottom  and  upland.  (Original.) 


LARGE-CAGE  EXPERIMENTS,  100G-7. 


57 


vations  have  been  made.  The  instruments  used  are  of  standard 
Weather  Bureau  type  (PI.  I,  fig.  1)  and,  as  the  records  extend  over 
several  years,  reliable  data  have  been  secured  upon  the  following 
climatic  factors  which  may  ailed  hibernation:  Maximum  and  mini- 
mum temperatures  supplemented  by  a  continuous  temperature 
record  made  by  a  recording  thermograph;  the  actual  rainfall  as  meas- 
ured in  a  standard  type  of  rain  gauge;  the  atmospheric  moisture  exist- 
ing at  8  or  9  o'clock  a.  m.  and  5  to  6  o'clock  p.  DL,  supplemented  by 
a  continuous  record  of  the  moisture  in  the  air  furnished  by  a  hygro- 
graph. 

Table  XXX.    (Jiitlim  of  hibernation  r.rp<  riments  in  1U0G-", •'. 


No. 
of  sec- 
tion. 


Date  of  starting  experiments 
in  l'JOO. 


Character  of  shelter  supplied. 


Food  supply. 


Dallas.  Calvert. 


Oct.  13 

Oct.  U 

Oct.  19 

Oct.  2.", 


Oct.  31 

Nov.  <; 

Nov.  12 

..do  

Nov.  •> 
Dec.  c, 
and  10. 


Oct.  13 
Oct.  19 
Nov.  2*> 
Oct.  25 


Oct.  31 

Nov.  6 

Nov.  M 
Nov.  12 
Nov.  2:, 
Dec.  3 


Victoria. 


Oct.  25    Leaves  and  grass.  4  to  .">  inches  ...   All  food  removed  after  two  days. 

..do  do   Stalks  cut  down  ami  left  to  dry. 

Oct.  SB   do   All  food  removed  after  twodays. 

Nov.  6    Spanish  moss  hung  on  string  at  '  Stalks  cut  down  and  allowed  to 

top  of  cage;  loose  bark  on  j  dry. 

ground. 

Nov.  in    Leaves  and  grass  4  to     inches    All  food  removed  after  two  days 
deep. 

Nov.  14   do   Cotton  cut  down  and  allowed  to 

dry. 

Nov.  21     Leaves  and  grass.  2  inches   l>o. 

..do         Leaves  and  grass,  10  Inches   Do. 

Nov.  2s    Q round  ahsolutelv  hare   No  food  supplv. 

Nov.  29  (a) 


1 1n  this  section,  i  bushels  of  probably  Infested  boDa  were  exposed  on  the  surface  of  the  ground  in  one  half 
of  cage,  and  3  bushels  were  buried  under  2  inches  of  - 1  i  rt  in  the  other  half. 

The  dates  given  in  Table  XXX  are  the  actual  dates  of  beginning 
the  ex])eriment  in  each  locality.  The  arrangement  of  the  experiments 
shown  in  the  table  is  primarily  chronological,  without  regard  to  the 
sequence  in  the  number  of  sections.  Some  knowledge  of  the  plan  of 
this  work  is  essential  to  a  clear  understanding  and  a  correct  interpreta- 
tion of  the  results  obtained  from  it. 


CLIMATIC  CONDITIONS   PRODUCING   HIBERNATION  AND   ACTIVITY  OF 
WEEVILS  DTJELNG   NORMAL  HIBERNATION  PERIOD. 

The  climatic  records  are  started  with  October  1,  1906,  in  order 
to  show  a  comparison  between  temperature  conditions  under  which 
weevils  are  normally  very  active  with  those  under  which  they  become 
inactive.  The  termination  of  what  is  considered  as  being  the  hiber- 
nation period  is  rather  arbitrarily  set  at  the  time  when  weevils  begin 
to  emerge  in  considerable  numbers.  It  should  be  stated  that  in  each 
locality  the  climatic  records  for  the  winter  of  1906  were  very  unusual. 
The  principal  points  of  variation  will  be  noted  in  subsequent  para- 
graphs in  their  most  important  connections.  In  each  chart  (figs.  3-5) 
showing  temperature1  conditions  it  has  been  deemed  advisable  to 
show  only  the  line  representing  the  mean  average  temperature. 


58 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


While  it  is  probable  that  a  study  of  maximum  and  minimum  tem- 
peratures is  really  more  accurate,  from  a  scientific  point  of  view, 
the  mean  average  temperature,  representing  one-half  of  the  sum  of 
the  maximum  and  minimum  for  each  day  will  be  sufficiently  exact 
and  a  more  simple  manner  of  expressing  the  relationship  existing 
between  temperature  and  weevil  activity.  The  significance  of  the 
term  "effective  temperature  "  has  previously  been  explained  (p.  24). 
Upon  the  temperature  charts  the  line  representing  43  degrees  is 
therefore  exceptionally  emphasized.  Wherever  the  temperature  line 
is  above  this  point  it  represents  effective  temperature.  Whenever 
it  falls  below  the  43-degree  line  it  is  possible  that  frosts  may  occur 
if  other  atmospheric  conditions  are  coincidently  favorable. 

Whenever  the  minimum  is  noted  to  be  32  degrees  or  below,  the 
actual  temperature  occurring  is  given  in  its  appropriate  place  upon 
the  record.  When  the  temperature  rises  above  80  degrees,  establish- 
ing a  new  maximum,  the  occurrence  is  also  shown  by  the  actual 
record  given  upon  the  charts. 

Since  it  is  impossible  for  weevil  emergence  to  occur  at  any  temper- 
ature below  43  degrees,  that  point  is  considered  as  initial  in  the  lines 
giving  the  records  of  the  activity  of  weevils.  The  actual  number  of 
weevils  found  active  at  various  dates  is  shown  at  the  top  of  the  line 
in  each  case. 

ENTRANCE  INTO  HIBERNATION. 

In  each  locality  there  occurred  a  considerable  decrease  in  tempera- 
ture during  the  month  of  October,  the  minimum  being  reached  about 
the  31st.  This,  however,  was  not  sufficiently  cold  to  cause  weevils  to 
hibernate  in  considerable  numbers.  During  the  following  two  weeks 
the  temperature  ranged  as  high  as  the  average  for  October.  After 
November  15,  however,  there  occurred  a  very  marked  fall  of  tem- 
perature, the  minimum  even  as  far  south  as  Victoria  establishing 
itself  at  about  25  to  27  degrees.  All  cotton  was  killed  by  this  freeze. 
The  count  of  weevils  found  active  early  in  November  indicated 
merely  that  few  weevils  had  entered  hibernation  at  that  time.  Fur- 
ther counts,  made  about  November  30,  showed  that  even  so  severe  a 
drop  in  temperature  as  had  occurred  did  not  immediately  drive 
weevils  into  hibernation.  During  the  succeeding  two  or  three  weeks 
the  temperature  again  ranged  fully  as  high  as  during  October,  and 
apparently  many  weevils  which  had  sought  shelter  after  the  freeze  of 
the  night  of  November  19  again  became  active.  This  was  indicated 
by  the  large  number  of  weevils  found  active  at  Calvert  and  Victoria 
about  December  10.  About  the  middle  of  December  another  period 
of  low  temperature  occurred,  which  was  followed  by  decreased  activity 
among  the  weevils,  many  of  which  did  not,  even  then,  seek  shelter. 
During  the  first  three  weeks  of  January  the  exceptionally  warm 
weather  experienced  throughout  Texas  drew  a  considerable  number 


60 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


LARGE-CAGE  EXPERIMENTS,  1900-7. 


CI 


62 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


of  weevils  from  shelter.  During  the  last  week  of  January  and  the 
first  week  of  February  the  lowest  temperatures  of  the  winter  occurred 
at  Dallas  and  Calvert.  The  counts  made  immediately  after  this 
period  showed  the  smallest  number  of  active  weevils  recorded  at  any 
time  during  the  winter  for  those  two  localities.  At  Victoria  the  tem- 
perature was  not  sufficiently  low  to  produce  any  marked  decrease  in 
weevil  activity.  During  the  remainder  of  February  there  was  a 
rather  steady  rise  in  temperature  throughout  the  State  and  many 
wreevils  continued  active.  The  figures  show  that  during  the  last 
week  of  the  month  considerable  numbers  were  emerging  from  their 
winter  shelter;  and  beginning  with  March  1  the  period  of  general 
emergence  is  considered  to  have  begun. 

While  these  three  charts  show  plainly  the  conditions  existing  during 
the  winter  of  1906-7,  proving  beyond  question  that  during  this 
season  there  was  no  such  thing  as  complete  hibernation  of  the  boll 
weevil  in  Texas,  it  must  not  be  understood  that  this  is  frequently  the 
case.  Xo  other  such  season  has  occurred  since  the  weevil  entered  Texas. 
As  a  rule,  hibernation  is  complete  during  the  period  of  from  four  to  six 
months.  It  is  certain  that  weevils  may  continue  their  activity 
throughout  the  season  wherever  climatic  conditions  are  not  sufficiently 
severe  to  entirely  destroy  the  growth  of  cotton. 

ACTIVITY  DURING  NORMAL  PERIOD  OF  HIBERNATION. 

The  general  impression  as  to  the  activity  of  weevils  during  the 
normal  period  of  hibernation  has  been  shown  in  figures  3  to  5.  A 
summary  of  the  records  for  the  three  locations,  with  the  temperature 
conditions  prevailing  at  the  time  of  each  examination,  is  shown  in 
Table  XXXI. 

Table  XXXX. — Activity  during  normal  hibernation  period,  1906-7. 

DALLAS. 


Date. 

Weevils  counted  in  section- 

Total 
weevils 
count- 
ed. 

Tempera- 
ture. 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

Max. 

Mean. 

1906. 

230 
62 

290 

102 

315 

937 

79 

°F. 

64.0 

Nov.  10  

96 

158 

86 

67.5 

Do  

4 

12 

12 
33 



28 

51 

38.0 

Nov.  28  

130 

1 

4 

7 

175 

62 

54.0 

Dec.  21  

5 

23 

19 

2 

15 

9 

11 

12 

18 

114 

66 

48.0 

Dec.  27  

8 

10 

48 
39 

5 

20 

8 

7 

19 

25 

150 

73 

64.0 

1907. 

Jan.  1  

9 

18 

7 

28 

13 

11 

43 

80 

248 

75 

69.5 

Jan.  12  

1.-) 

24 

68 

15 

33 

15 

15 

55 

70 

310 

82 

68.0 

Jan.  24  

4 

5 

26 

3 

17 

9 

21 

4 

16 

1  1 

109 

73 

48. 5 

Feb.  12  

1 

4 

5 

2 

4 

4 

1 

22 

2 

54 

61 

45.0 

Feb.  19  

3 

4 

7 

3 

21 

7 

11 

5 

SO 

9 

123 

SO 

66. 0 

Total  

341 

486 

341 

140 

1SS 

32 

:w» 

57 

217 

2  IS 

« 2,406 

a  This  total  represents  7.S  per  cent  of  all  the  weevils  put  in  the  cage. 


LABGE-CAGE  EXPERIMENTS,  l'JOti-7.  03 


Table  XXXI. — Activity  (hiring  normal  hibernation  period,  1906-1 — Continued. 

CALVERT. 


Date. 

Weevils  counted  in  gwjtlun- 

Total 
weevils 
count- 
ed. 

Tempera- 
ture. 

1 . 

3. 

4. 

5. 

G. 

7. 

■ 
o. 

in 

IV. 

Max. 

Moan. 

1906. 

Nov.  17  

17 

28 
9 

233 
6 

28 
6 

161 

467 

•jr. 

oF 

Nov  29 

3 

214 

55 

10 

139 

442 

397 

Dec  .  22  

4 

47 

68 

30 

4 

8 

217 

0 

17 

69 

1 

60 

48.0 

1907. 

Jan.  14  

11 

41 

90 

3 

12 

.50 

2 

299 

82 

70.0 

Jan.  21  

3 

30 

22 

1 

j 

63 

I 

4 

20 

159 

62 

47.0 

Jan.  2S  

1 

13 

7 

1 

3 

37 

1 

5 

17 

86 

56 

39.0 

Feb.  11  

3 

12 

5 

0 

1 

28 

1 

4 

21 

0 

75 

75 

52.0 

Feb.  18  

1 

13 

6 

0 

2 

43 

2 

2 

a 

0 

91 

79 

62. 0 

Feb.  25  

3 

10 

1 

0 

| 

36 

1 

1 

0 

69 

74 

65.0 

Total  

46 

4H7 

m 

61 

272 

514 

44 

216 

349 

5 

a2,085 

VICTORIA 


1906. 

Nov.  25  

133 

204 

m 

496 

71 

66.5 

Pec.  10  

345 
163 

504 

64 

546 

323 

1 . 783 

73 

59.5 

Pec.  19  

236 

19 

lis 

47 

40.0 

Pec.  21  

62 

95 

66 

186 

81 

18 

200 

708 

65 

51.5 

1907. 

Jan. 7  

lus 

134 

11 

253 

77 

73.0 

Jan.  14  

147 

68 

89 

•12 

106 

404 

77 
66 

72.  i) 

Jan. 21  

50 

HI 
89 

27 

69 

76 

16 

106 

lv. 

5 

?29 

Feb.  4  

48 

55 

40 

85 

46 

43 
18 

67 

123 

3 

5'.H» 

60 

50. 0 

Feb.  18  

55 

40 

91 

21 

65 
66 

46 

29 

3 

442 

74 

62.  0 

Feb.  26  

49 

13 

31 

50 

312 

70 

66.  5 

Total  

562 

m 

3ss 

975 

386 

2m 

94S 

1,079 

41 

6  6.143 

i  This  total  represents  10.5  j>er  cent  of  all  the  weevils  put  in  the  cape. 
This  total  represents  27.7  per  cent  of  all  wee\  ils  put  in  the  <  me. 


It  is  hardly  probable  that  a  majority  of  the  weevils  may  have 
been  counted  upon  two  or  more  dates,  but  the  fact  that  dead  weevils 
Were  found  clinging  to  the  wire  (PI.  VII.  fig.  1)  at  the  time  of  each 
examination  indicates  a  considerable  mortality  among  the  active1 
weevils  and  that  the  places  of  the  dead  ones  in  successive  counts 
were  taken  by  weevils  which  had  become  active  since  the  preceding 
examination.  The  percentages  of  active  weevils  for  the  three  local- 
ities show  a  rather  significant  (liil'erence.  and  are  given  for  the  sake 
of  this  comparison  without  presuming  to  state  correctly  the  actual 
percentage  of  weevils  placed  in  hibernation  which  remained  active 
during  the  winter  in  the  respective  localities.  At  Dallas  the  2,400 
weevils  counted  during  the  winter  constitute  7.8  per  cent  of  the  total 
number  placed  in  hibernation.  At  Calvert  the  2,085  active  weevils 
constitute  10.5  per  cent  of  the  10,408  placed  in  the  cage.  At  Vic- 
toria the  6,1  13  active  weevils  constitute  27.7  per  cent  of  the  22,463 
in  the  experiment.  Since  approximately  the  same  number  of  exam- 
inations were  made  in  each  locality  the  differences  in  percentage 
indicate  in  a  general  way  the  relative  activity  in  these  sections  of 


64 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


the  State.'  Thus  at  Dallas  8,  at  Calvert  11,  and  at,  Victoria  28  out 
of  every  100  weevils  placed  in  hibernation  might  have  been  active 
during  the  winter.  Of  course,  it  is  likely  that  many  weevils  were 
counted  twice.  On  the  other  hand,  to  counterbalance  this  duplica- 
tion in  the  number  recorded,  it  should  be  stated  that  undoubtedly 
many  weevils  were  active  at  intervals  between  the  counts  which 
were  either  upon  the  ground  or  had  returned  to  the  ground  before 
the  examinations  were  made.  Only  those  weevils  which  were  found 
crawling  upon  the  wire  covering  of  the  cage  were  recorded.  The 
temperature  conditions  as  shown  for  the  dates  of  examination  indi- 
cate that  there  would  be  no  physiological  difference  in  normal  weevil 
activity  upon  those  dates.  The  sectional  totals  indicate  that  vari- 
ations in  the  class  of  shelter  in  the  different  sections  exerted  little, 
if  any,  effect  upon  the  activity  of  weevils  during  the  winter,  with 
the  exception  that  Spanish  moss  seemed  to  keep  more  weevils  from 
becoming  active  than  did  any  other  shelter. 

WINTER  ACTIVITY. 

In  most  instances  when  the  active  living  weevils  were  recorded 
those  which  were  found  dead  clinging  to  the  wire  were  collected 
and  counted  for  each  section.  Undoubtedly  a  great  many  weevils 
fell  from  the  screen  before  or  after  dying,  so  that  the  records  are 
very  conservative  in  showing  the  mortality  occurring  between  exam- 
inations. These  records  should  be  considered  in  connection  with 
weevil  activity,  since  the  collection  of  dead  stages  prevented  their 
accumulation  upon  the  wire,  and  the  number  found  at  each  exam- 
ination must  be  considered  of  those  surviving  and  remaining  on  the 
wire  from  a  preceding  examination  and  those  which  emerged  subse- 
quently thereto. 

Table  XXXII. — Summary  of  winter  activity  as  shown  by  counts  of  dead  weevils. 

DALLAS. 


Number  of  dead  weevils  found  in  section—  ,  1  Total 
 |  num- 


Date. 

1. 

2. 

3. 

4. 

5. 

0. 

7. 

8. 

9. 

10. 

ber 
of 
dead 
wee- 
vils. 

1907. 

2 
0 
2 
1 

3 
2 

3 

4 

1 

34 
2 
2 
5 
3 

10 

10 

4 

75 
3 

"  t»S7 
38 
13 

January  12  

January  24  

2 
4 

3 

□  072 
7 

2 
0 
3 

5 
7 
1 

February  12  

February  19  

1 
1 

3 
1 

1 

Total  

5 

9  |  13 

3  40 

080 

14 

8 

17 

l>  S10 

•  Of  these.  (.22  were  on  clot  li  on  ground,  having  fallen  from  I  lie  wire. 
t>  This  total  represents  2.0  per  cent  of  all  the  weevils  put  in  the  cage. 


Bui.  77,  Bureau  of  Entomology.  U.  S.  Dept.  of  Agriculture, 


Plate  VII. 


Shelter  Conditions,  Dallas,  Tex.,  Cage. 

Fi#.  i.— Active  weevils  trying  to  escape  through  wire  on  October  20,  1906.  Pig.  2.— Section  l.  in 
which  weevils  were  placed  October  13,  L906,  £61  percent  surviving.  Fig.  3.— Section  1.  started 
October  16,  1906,  4.07  per  cent  surviving.  (Original.) 


LARGE-CAGE  EXPERIMENTS,  1906-* 


65 


Table  XXXII. — Summary  of  winter  activity  as  shown  by  counts  of  dead  weevils — Con. 

CALVERT. 


Number  of  dead  weevils  found  in  section 

— 

Total 
num- 

Date. 

L 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

ber 
of 
dead 
wee- 
vils. 

1906. 

121 

36 

83 

6 

47 

293 

14 

2 

101 

7 

39 

2 

20 

34 

220 

December  22  

1 

3 

16 
3 

7 

5 

2 

0 

4 

7 

2 

47 

1907. 

5 

4 

2 

5 

10 

0 

3 

10 

1 

43 

0 

12 

5 

12 

0 

0 

6 

0 

35 

January  28  

0 

0 

0 

0 

1 

February  11  

0 

5 

5 

2 

0 

ia 

0 

3 

3 

0 

30 

February  18  

1 

4 

3 

0 

0 

4 

0 

2 

9 

23 

February  25  

1 

0 

0 

0 

1 

0 

8 

2 

Total  

143 

18 

.4. 

54 

137 

41 

9 

79 

69 

3 

a  094 

VICToltl  \. 


1906. 

8 

13 

14 

35 

2 

6 

2 

16 

29 

3 

! 

0 

5 

December  24  

3 

7 

19 

11 

5 

6 

51 

1907. 

0 

0 

0 

0 

January  14  

3 

4 

6 

2 

14 

January  21  

6 

10 
8 

12 

6 

12 

4 



2 

12 

5 

2 

71 

9 

9 

2 

ID 

2 

u 

11 

67 

February  18  

6 

2 

7 

8 

4 

1 

0 

12 

11 

0 

51 

9 

u 

4 

5 

11 

5 

0 

45 

Total  

44 

55 

37 

59 

54 

13 

60 

32 

3 

«>368 

"  This  total  n-prrsents  :(  1',  jmt  (•••nt  of  ;ill  th<>  wifvils  put  in  the  ca^e. 
b  This  total  represents  1.7  i>er  cent  of  all  the  weevils  put  in  the  cage. 

In  the  section  of  the  table  containing  the  records  for  Dallas  the 
large  number  of  weevils  found  dead  in  section  f>  on  January  24,  1907, 
may  be  explained  by  the  statement  that  no  previous  collection  of 
dead  weevils  had  been  made  in  this  section.  All  but  50  of  the  wee- 
vils found  were  upon  cheesecloth  stretched  horizontally  across  the 
section  above  the  ground.  The  full  number  is  included  merely  to 
indicate  the  proportion  of  weevils  which  probably  fall  to  the  ground 
upon  dying.  In  this  section  less  than  20  per  cent  remained  upon 
the  screen,  and  it  is  reasonable  t<>  suppose  thai  a  similar  proportion 
may  have  existed  in  other  sections.  The  percentage  of  mortality  in 
each  place  is  much  smaller  than  the  percentage  of  living  weevils. 
I'pon  the  charts  shown  in  figures  3  to  5  the  number  of  dead  collected 
is  indicated  by  a  broken  line  extending  beyond  the  line  representing 
the  number  of  living  weevils. 
90317— Ball.  77—09  5 


66 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


ACTIVITY  AS  SHOWN  BY  DEVELOPMENT  DURING  NORMAL  HIBERNATION 

PERIOD. 

Under  the  heading  " Stages  entering  hibernation"  the  principal 
data  bearing  upon  developmental  activity  during  the  winter  have 
been  given.  (See  pp.  13  and  14.)  Additional  data  have  also  been 
given  in  connection  with  "Shelter  during  hibernation."  (See  Table 
VII,  p.  26;  also  Table  IX,  p.  28.)  To  these  records  for  seasons  pre- 
ceding 1906-7  may  be  added  the  results  of  an  experiment  in  collec- 
tion of  infested  squares  during  tins  season.  On  November  23,  1906, 
Mr.  J.  D.  Mitchell  collected  100  fallen  squares  which  were  supposed 
to  be  infested.  These  were  placed  in  the  small  cage  under  shelter 
and  out  of  the  reach  of  sunshine.  On  February  10,  1907,  he  found 
that  45  squares  showed  weevil  emergence  hulls,  and  the  full  number 
of  adults  was  found;  however,  all  were  dead  at  that  time.  An  exam- 
ination of  the  remainder  of  the  squares  revealed  but  one  dead  larva, 
The  others,  apparently,  had  contained  no  weevil  stages.  Exception- 
ally warm  weather  had  prevailed  during  December  and  January,  as 
has  been  shown  in  figure  5.  This  had  enabled  the  weevils  to  com- 
plete their  development  and  emerge,  but  all  had  starved  to  death  in 
the  absence  of  any  food  supply. 

Some  very  interesting  facts  are  also  brought  out  by  a  closer  study 
of  the  records  in  connection  with  section  10  of  each  cage.  As  has 
been  shown,  the  experiment  in  these  sections  consisted  of  the  collec- 
tion of  large  numbers  of  unopened  bolls  probably  infested.  Several 
of  the  bolls  were  buried  under  2  inches  of  dirt  and  the  remainder 
were  exposed  upon  the  surface  of  the  ground  (PL  X,  fig.  1).  No 
partition  was  inserted  to  separate  the  weevils  emerging  from  these 
two  lots  of  bolls,  but  in  the  case  of  section  10  at  Dallas  the  first  lot 
of  bolls  was  buried  and  a  considerable  period  elapsed  before  the  bal- 
ance of  the  bolls,  which  were  left  upon  the  surface,  was  placed  in 
the  cage.  It  was  estimated  that  3,000  bolls  were  buried  at  a  uniform 
depth  of  2  inches  under  cover  of  heavy  black  soil.  An  examination 
of  100  bolls  showed  8  recently  transformed  but  unemerged  adults  in 
the  bolls  and  8  adults  which  had  emerged  were  hibernating  within 
the  protection  afforded  by  the  bolls.  On  this  basis  it  appears  that 
about  480  weevils  were  buried  in  this  lot  of  3,000  bolls,  half  of  them 
being  unemerged  adults  and  half  hibernating  adults.  No  other  mate- 
rial was  placed  within  this  section,  so  that  all  weevils  which  were 
subsequently  found  upon  the  screen  must  necessarily  have  found 
their  way  through  the  2  inches  of  soil  under  which  the  bolls  were 
buried.  Counts  made  before  the  bolls  to  be  placed  on  the  surface 
were  put  into  the  cage  showed  that  65  weevils  at  least  had  escaped 
from  the  bolls  to  the  screen  forming  the  cage.  This  shows  that  fully 
L3.5  per  cent  of  all  the  weevils  buried,  emerged  and  unemerged,  had 


EMERGENCE  FROM  HIBERNATION,  1907. 


67 


succeeded  in  escaping,  Fndoubtedly  part  of  these  had  left  their 
cells  in  the  bolls  alter  they  were  buried,  as  it  is  very  likely  that  the 
burial  of  the  bolls  in  moist  soil  may  soften  the  hulls  so  as  to  enable 
the  weevils  to  escape  through  them  as  readily  as  though  they  remained 
dry  upon  the  surface  of  the  ground. 

ACTIVITY   IN   THE   FIELD  DUBING   NORMAL  HIBERNATION  PERIOD. 

For  a  number  of  years  it  has  been  known  that,  ID  southern  Texas 
especially,  weevils  may  frequently  be  found  moving  actively  in  the 
field  during  the  winter,  but  the  observations  made  during  the  season 
of  7  extended  the  range  of  such  occasional  activity  even  in 

northern  Texas. 


Table  XXXIII. — Outdoor  activity  of  wet  i  Us  during  winter  of  1906-7. 


Locality. 

Date. 

Weevlla 

found. 

Sprout 
plant  s 
exam- 
ined. 

Remarks. 

1907. 

Dallas.  Tex  

Jan.  1 

1 

Found  on  awntng  r« >i >«■. 

Do  

Jan.  11 

1 

Found  on  window  screen;  temperature  74"  F. 

no.  ia 

1 

Found  on  outside  of  hibernating  cage;  tempera- 

ture 7')°  F. 

College  Station,  Tex.... 

Feb.  23 

1 

Do. 

Do  

Jan.  17 

2 

Feeding  on  sprout  cotton. 

l'.KHi. 

Victoria,  Tex  

Dec.  29 

When  given  sprouts,  all  were  feeding  in  SO  min- 

utes; temperature  B2°  F. 

Do  

...do  

11) 

When  given  sprouts,  all  were  feeding  in  <:>  min- 

utes; temperature  si!"  F. 

1907. 

Do  

Jan.  B 

9 

(«) 

Me;iu  temperature.  Januarv  1  s,    ti7.7<>°  F. 

Do  

Jan.  9 

20 

M 

<> 

On  black  (and. 

Do  

Jan.  II 

7 

Do  

Jan.  10 

1 

so 

II)  weevils  In  bolls  on  the  same  plant. 

Do  

...do  

2 

30 
8 

Do  

Jan.  it 

~\ 

Do  

Jan.  IK 

1 

17 

Do  

Pen.  u 

1 

2'y 

Upland  sprouts  not  killed  as  in  bottoms. 

Do  

Feb.  w 

:\ 

80 

Very  dry  for  sprout  growth. 

a  Record  not  kept,  though  plants  frere examined. 

1  Sprout  cotton  on  six  farms  examined. 


From  the  "\'i<-t < records  it  appears  that  between  January  8  and 
February  21,  at  a  time  when  weevils  should  normally  have  been  in 
complete  hibernation,  48  adults  were  found  feeding  on  about  200 
sprout  plants.  This  record  is  unique  for  the  United  States,  and  a 
similar  activity  in  the  field  may  not  be  duplicated  except  under  very 
rare  conditions. 

EMERGENCE  FROM  HIBERNATION,  1907. 

As  is  plainly  shown  by  figures  3  to  5,  the  actual  period  of  general 
emergence  from  hibernation  began  in  each  locality  about  February  20. 
As  has  been  previously  stated,  the  actual  date  of  the  beginning  of 
emergence  can  not  be  positively  given.  It  can  be  better  expressed 
as  a  period  of  ''beginning  emergence,"  and  for  this  reason  this  period 
seems  to  lie  between  February  20  and  March  1.    Owing  to  the  excep- 


68 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


tional  earliness  of  the  season  preparations  for  the  regular  observations 
upon  emergence  from  hibernation  were  not  sufficiently  complete  for 
beginning  the  work  until  March  1  and  in  each  locality  this  date  may 
very  reasonably  be  considered  as  the  beginning  of  the  emergence 
period. 

Previous  experience  having  demonstrated  the  necessity  of  keeping 
the  records  upon  this  work  according  to  a  uniform  system  in  each 
locality,  the  preparations  were  much  more  elaborately  made  than  for 
any  previous  work.  Comprehensive  forms  upon  which  the  records 
might  be  entered  with  a  minimum  of  labor  were  prepared  covering 
five  distinct  divisions  of  the  work:  (1)  Meteorological  record;'  this 
record  covered  maximum  and  minimum  temperatures,  atmospheric 
humidity,  rainfall,  sunshine  or  cloudiness,  and  winter  conditions. 
(2)  Emergence  record;  this  record  showed  the  emergence  in 'each 
section  for  each  date.  The  records  for  one  week  were  placed  upon  a 
card  so  that  the  totals  for  emergence  for  each  day,  and  also  for  each 
section  for  each  week,  could  be  very  readily  ascertained.  (3)  Section 
record;  this  covered  in  more  detail  the  emergence  in  each  section 
and  indicated  the  sex  of  emerging  weevils  and  what  disposition  was 
made  of  them,  in  such  a  way  that  their  records  could  be  followed  until 
the  time  of  death.  (4)  Longevity  records  for  fed  weevils.  (5)  Lon- 
gevity records  for  unfed  weevils. 

This  systematization  of  the  record  work  has  proved  an  invaluable 
help  in  compiling  the  results  of  this  extensive  series  of  observations. 
The  general  facts  regarding  the  relationship  existing  between  climatic 
conditions  and  weevil  emergence  are  indicated  graphically  in  figures 
6  to  8.  The  most  important  conclusions  upon  special  points  can  only 
be  shown  by  special  arrangements  of  the  data  in  each  case.  These 
tables  have  been  made  as  concise  as  seems  possible.  Practically  each 
line  in  the  tables  expresses  only  the  summary  of  a  large  number  of 
compiled  records.  The  magnitude  of  the  work  involved  in  the  com- 
pletion of  such  data  can  be  appreciated  only  by  one  who  has  under- 
taken a  similar  task.a 

RELATIONSHIP  OF  EMERGENCE  FROM  HIBERNATION  TO  CLIMATIC  CON- 
DITIONS. 

Figures  6  to  8  have  been  prepared  in  the  same  form  as  figures  3  to 
5,  since  they  express  a  continuation  of  similar  facts. 

In  former  reports^  dealing  especially  with  the  life  history  of  the 
boll  weevil,  it  was  stated  that  emergence  began  about  the  time 
when  the  mean  temperature  rose  above  60°  F.    The  more  complete 

"  Tin;  senior  author  desires  to  express  particular  appreciation  of  the  great  amount  of 
detail  work  which  lias  been  done  by  the  junior  author  (Mr.  W.  W.  Yothers)  in  the  prep- 
aration of  the  summaries  covering  this  work. 

b\J.  S.  Dept.  Agr.,  Bur.  Ent.,  Buls.  45  and  51. 


EMERGENCE  FROM  HIBERX  ATK  >N  ,  1907. 


69 


records  now  at  hand  indicate  that  emergence  may  take  place  when- 
ever the  mean  average  temperature  exceeds  5o°  F.  It  is  certain 
that  weevils  may  he  active  at  a  temperature  considerably  lower 
than  this,  but  the  records  do  not  indicate  that  there  is  a  general 


emergence  from  hibernation  at  a  lower  temperature.  After  having 
left  their  winter  quarters,  weevils  may  continue  active  at  considerably 
lower  temperatures  than  are  required  to  draw  them  out  from  their 
shelter.    This  statement  may,  in  part  at  least,  explain  the  continued 


70 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


activity  of  weevils  during  the  winter  of  1906-7  and  the  early  beginning 
for  the  period  of  emergence  for  that  season. 


S     8     3     §  S 

<\i          <M  — •          —  O 

N 
k 

s 

O 

Si 

rvi  1 

i>        o         o        o  O 

s    s     §  as 

\J        —         —         O  | 

1/  N/  -7-H&Nir±/ 

A  comparison  of  figures  6,  7,  and  8  indicates  that  the  period  of  great- 
est emergence  in  each  locality  occurred  during  March,  1907.  The 
abnormal  nature  of  temperature  conditions  is  shown  by  the  fact  that 


EMERGENCE  FROM  HIBERNATION,  1907. 


71 


at  Dallas  the  mean  average  temperature  for  the  month  was  over  11 
degrees  above  the  normal.    At  Calvert  the  departure  was  about  the 


ffA/MFALL  /I 

s 

o 

RAIN, 

o  — 

5     S  <5 

^ALL  /N  /NCHES 

same,  and  at  Victoria  it  was  but  slightly  less  than  10  degrees  above 
normal.  Such  high  temperatures  do  not  often  occur  before  the  latter 
part  of  April  and  the  1st  of  May.    The  temperature  for  April  was 


72 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


unusually  unfavorable,  but  in  all  sections  it  ranged  from  3  to  5 
degrees  below  the  normal.  This  decrease  was  not,  however,  sufficient 
to  check  the  emergence  of  weevils,  although  undoubtedly  it  served  to 
extend  the  period  of  emergence  in  an  unusual  degree.  The  abnormal 
nature  of  the  temperature  conditions  for  the  spring  of  1907  may  be 
understood  from  a  comparison  of  the  mean  monthly  temperatures  for 
these  four  months  in  each  case.  The  normal  is  determined  by  the 
Weather  Bureau  records  from  an  average  of  the  mean  monthly  tem- 
peratures for  the  entire  period  during  which  records  are  available. 
The  departure  of  each  season,  therefore,  affects  the  normal  for  the 
following  season. 

The  general  impression  in  regard  to  the  exceptionally  high  tem- 
perature experienced  during  the  winter  of  1906-7  is  confirmed  by  a 
comparison  with  the  average  records  for  a  number  of  seasons.  Tem- 
perature alone  need  be  considered  in  making  this  comparison,  although 
rainfall  has  an  important  direct  effect  upon  temperature  conditions. 
For  the  following  comparison  the  records  given  by  the  United  States 
Weather  Bureau  are  used.  As  there  is  no  report  for  Calvert  the 
average  of  two  points  about  equally  distant  on  opposite  sides  of  that 
place  is  used. 


Table  XXXIV. — Mean  monthly  temperatures  and  departures  from  normal  at  Dallas, 
Calvert,  and  Victoria,  Tex.,  November,  1906,  to  February,  1907. 


November. 

December. 

January. 

February. 

Locality. 

Monthly 

Depar- 

Monthly 

Depar- 

Monthly 

Depar- 

Monthly 

Depar- 

mean. 

ture. 

mean. 

ture. 

mean. 

ture. 

mean." 

ture. 

°F. 

°F. 

•jr. 

°F. 

°F. 

°F. 

•jr. 

°F. 

Dallas  

54.3 

-0.6 

51.6 

+3.8 

53.4 

+8.5 

51.2 

+6.6 

Calvert  

59.1 

+  .1 

56.8 

+4.1 

59.8 

+  9.6 

54.8 

+  2.8 

Victoria  

62.9 

-,s 

59.2 

+  1.4 

63.4 

+  9.8 

60.2 

+  6.2 

It  will  be  noted  that  the  departure  from  normal  during  November 
was  very  slight.  The  temperature  conditions,  therefore,  during  the 
usual  period  of  entrance  into  hibernation  were  practically  normal,  the 
rise  occurring  during  December  and  January,  especially  when  weevils 
should  normally  have  been  in  complete  hibernation.  Table  XXXV 
continues  the  same  study  throughout  the  period  of  emergence  from 
hibernation. 


Table  XXXV. — Mean  average  temperatures  and  departures  from  normal  at  Dallas, 
Calvert,  and  Victoria,  Tex.,  March  to  June,  1907. 


Locality. 

March. 

April. 

May. 

June. 

Monthly 
mean. 

Depar- 
ture. 

Monthly 
mean. 

Depar- 
ture. 

Monthly 
mean. 

Depar- 
ture. 

Monthly 
mean. 

Depar- 
ture. 

•jr. 

•jr. 

•jr. 

•jr. 

•jr. 

•jr. 

•jr. 

•jr. 

Dallas  

66.7 

+11.1 

61.4 

-4.2 

65.8 

-7.7 

78.8 

-1.9 

Calvert  

70.0 

+  9.2 

62.2 

-5.9 

66.6 

-7.3 

76.6 

-4.4 

Victoria  

72.4 

+  9.7 

69.4 

-3.3 

73.0 

-5.0 

81.6 

-  .6 

EMERGENCE  FROM  HIBERNATION,  1007. 


73 


The  unprecedented  emergence  during  March  is  very  easily  explained 
by  the  remarkable  temperature  conditions  during  that  month.  In 
spite  of  the  fact  that  emergence  began  earlier  than  had  ever  been 
known  previously,  it  continued  later  also  because  of  the  exceptionally 
low  temperatures  prevailing  during  April,  May,  and  June.  A  com- 
parison of  figures  1  and  2  with  figures  6  to  8  is  interesting  and  shows 
how  strikingly  the  nature  of  the  emergence  movement  may  vary  in 
respect  to  difference  in  climatic  conditions.  The  careful  examina- 
tions made  to  discover  the  termination  of  the  emergence  period  were 
continued  for  fully  two  weeks  after  the  last  weevil  was  found.  It 
seems  impossible  to  explain  the  long-delayed  emergence  of  some 
individuals.  The  lack  of  an  explanation,  however,  does  not  alter  the 
fart  that  emergence  is  probably  not  generally  complete  until  after  the 
middle  of  June. 


Tahi.i:  XXXVI.    (i<mruJ    summary  of  (  r  peri  men  fs  of  on  emergence  from 

hibt  mat  ion. 


Locality. 

Number  df 
weevils — 

Number 

of  wce- 
vils 
emer- 
ging 

Peroent< 
age 
emer- 
ging. 

Put  in 

cages. 

I'sed  as 
basis  for 
percent- 
age of 
emer- 
gence.<i 

32. 439 
20. 430 
23,i  Vi:> 

30.  NM 
19.408 
22.  161 

3,464 
1.842 
6  3. 026 

11.22 
9.49 
13.47 

Victoria,  Tex  

Total  and -average  

76,514 

72. 735 

8.332 

11.45 

"Basis  for  computing  the  |>crccntage  of  emergence  is  5  per  cent  less  than  the  number  of  weevils  put  in 
cages  owing  U)  the OBOape  of  some  weevils  through  the  meshes  of  the  wire. 
6  Two  weevils  not  in  summary. 


A  deduction  of  5  per  cent  from  the  number  of  weevils  placed  in  the 
hibernation  experiments  is  made  to  furnish  a  more  correct  basis  for 
determining  percentages,  on  account  of  the  fact  that  experiments 
have  shown  that  about  5  per  cent  of  a  miscellaneous  collection  of 
weevils  may  be  able  to  escape  through  14-niesh  wire  (PI.  VII,  fig.  1), 
such  as  was  used  in  the  construction  of  these  cages.  The  percentage 
of  survival  is  strikingly  similar  in  each  locality.  The  average  sur- 
viving hibernation — approximately  11  per  cent — is  probably  the 
highest  that  has  ever  occurred  since  the  weevil  entered  Texas. 
Although  observations  have  indicated  that  occasionally  the  per- 
centage of  survival  may  be  as  high  as  this  in  the  held,  it  is  fortunate 
for  the  cotton  planter  that  such  is  very  rarely  the  case. 


74 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


EFFECT  OF  TIME  OF  ENTERING  HIBERNATION  AND  NATURE  OF  SHELTER 
UPON  THE  PERCENTAGE  OF  SURVIVAL. 

One  of  the  most  important  points  upon  which  information  was 
sought  throughout  these  experiments  was  the  effect  of  time  of  enter- 
ing hibernation  and  nature  of  shelter  upon  the  percentage  of  survival. 
The  first  confinement  of  weevils  in  the  fall  occurred  fully  a  month 
earlier  than  the  beginning  of  similar  experiments  the  previous  year, 
and  it  was  expected  that  the  intervals  between  their  confinement  in 
the  cage  and  the  time  for  successful  hibernation  might  be  sufficient  to 
plainly  reduce  the  proportion  of  weevils  surviving. 

Table  XXXVII. —  Chronological  arrangement  of  sectional  records  shotting  relative 
survival  at  Dallas,  Calvert,  and  Victoria,  Tex.,  1906-7. 

DALLAS. 


See- 
When  tion 
started,  num- 
\  ber. 


Character  of  shelter  and  food. 


Date  of 
last 
emer- 
gence. 


Basis 
number 
of 

weevils. 


Total 
weevils 


Percent- 
age of 


emerged,  survival. 


Rank  of 
section  in 
survival. 


1906. 
Oct.  13 


Oct.  16 
Oct.  20 


Oct.  24 
Oct.  30 


Nov. 


Nov.  12 
Nov.  13 


Nov.  15 


Nov.  21 
Nov.  28 


Dec. 


Leaves  and  hay,  4  inches  deep,  cot- 
ton stalks  left  a  

Leaves  and  hay;  stalks  cut  and  left 
four  days  b  

Leaves  and  grass  4-5  inches  deep; 
no  food  

Spanish  moss  and  chips; c  cut  food. 

Leaves  and  grass  2-3  inches  deep; 
no  food  d  

Leaves  and  grass  9-10  inches  deep; 
stalks  cut  and  left  «  

Leaves  and  grass:  no  food  /  

Leaves  8-10  inches  deep;  green  cot- 
ton cut  and  left  g  

Leaves  3-4  inches  deep:  stalks  left 
standing  

 do  

Bare  ground;  no  food  

[Bolls  i  on  surface  j  

i Bolls '  buried;  


1907. 

May  21 

May  6 

May  19 
June  17 

,  June  15 

'  May  15 
I  May  21 

June  19 

June  4 
June  8 
i  Apr.  29 

Way  2 


3,800 

2,090 

3,610 
3,325 

2,850 

3,135 
3,040 

3,040 

2,565 
1,570 
975 


99 

85 

226 
231 

250 

383 
448 

788 

804 
65 
46 

39 


Total  and  average   30,864  ) 


2.61 

4.07 

6.  26 
6.95 

8.  85 

12.22 
14.  74 

25.92 

31.  34 
h  4. 14 
4.  72 

4.51 


CALVERT. 


Oct. 

13 

1 

Food,  two  days;  grass  and  leaves 

4-5  inches  deep  

June 

12 

2,375 

75 

3. 15 

Oct. 

19 

4 

Grass  and  leaves  4-5  inches  deep  

May 

30 

2,375 

116 

4.88 

5 

Oct. 

25 

7 

Spanish  moss;  chips  

July 

1 

2,375 

105 

4.42 

6 

Oct. 

31 

8 

Food  two  days;  grass  and  leaves  4-5 

inches  deep  

May 

30 

2,375 

63 

2.  65 

8 

Nov. 

5 

5 

Food  dry;  grass  and  leaves  4-5 

inches  deep  

Apr. 

26 

2,375 

45 

1.89 

9 

Nov.  12 

9 

Food  cut  down,  left  dry;  10  inches 

grass  and  leaves  

June 

12 

2,375 

438 

18.  44 

3 

Nov. 

14 

3 

Stalks  cut  down,  left  dry;  2  inches 

grass  and  leaves  

May 

31 

2,375 

253 

10.  65 

4 

Nov. 

25 

6 

Field  protection  or  bare;  some  grass. 

Mav 

16 

1,425 

359 

25. 19 

2 

Nov. 

26 

2 

Xo  food;  leaves  and  hay  •.  

June 

12 

1,358 

380 

27.98 

1 

Dec. 

3 

10 

Bolls  

Mar. 

24 

(*) 

8 

10 

Total  and  average  

19,408 

1,S42 

9.  49 

a  See  PI.  VII,  fig.  2. 
t>See  PI.  VII,  fig.  3. 
eSee  PL  VIII,  figs,  l,  2. 
dSee  PL  IX,  fig.  1. 
e  See  PI.  IX,  fig.  2. 
/See  PI.  IX,  fig.  3. 
o See  PI.  X,  fig.  2. 

h  The  weevils  put  in  on  November  21  were  brought  from  Brownsville,  Tex.    The  low  percentage  of 
survival  doubtless  resulted  from  their  weakened  condition,  owing  to  Insufficient  food  during  transportation. 
i  Bolls  presumably  infested. 
;  Sce  II  X.  fig.  1. 
*  No  estimate  made. 


Bui.  77,  Bureau  of  Entomology  U.  S.  Dept.  of  Agriculture 


Plate  VIII. 


Hanging  Moss  as  Affecting  Hibernation  and  Emergence. 

Fig.  1.— Section  7,  with  hanging  moss  in  top  of  cage.    Fig.  2.— Same  sec  tion,  ground  conditions, 
started  October  24,  19015;  t>.95  per  cent  surviving;  emergence  ceased  June  17,  1907.  (Original.) 


Bui.  77,  Bureau  o*  Entonrv 


U  S  Dept.  of  Agriculture 


Plate  IX. 


Shelter  Conditions  Producing  Average  Survival  at  Dallas,  Tex. 

tig.  1.— Section  8.  started  October  30.  1906;  emergence  ceased  June  16,  1907:  survival.  8.86  per 
cent.  Fig.  J.— Section  5,  started  November  o.  190t'»:  emergence  ceased  May  In.  1907:  survival. 
12.22  per  cent.  Fig.  3.— Section  started  November  12,  1900;  emergence  ceased  May  21,  1907: 
survival.  14.74  per  cent.    |  Original.) 


Bui.  77,  Bureau  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


Plate  X. 


Exceptionally  Favorable  Conditions  and  Boll  Experiment. 

fig.  L. — Section  10.  a,  bolls  exposed  on  surface;  6,  corner  where  bolls  were  buried  2  inches 
deep,  started  December  t),  190t>;  emergence  ceased  Mav  J.  1907:  survival.  4.51  per  cent.  Fig.  2.— 
Section  9.  stalks  left,  started  November  13, 190*1:  emergence  ceased  .June  19.  1907:  survival.  26.92 
percent.  (Original.) 


EMERGENCE  FROM  HIBERNATION,  190". 


75 


Table  XXXVII. — Chronological  arrangement  oj  sectional  records  sho icing  relative  sur- 
l  ival  at  Dallas,  Calvert,  and  Victoria,  Tex.,  1906-7 — Continued. 

VICTORIA. 


See- 
When  tion 
started,  num 
l>er. 


190ti. 
Oct.  25 
Do. . . . 

Oct.  28 

Nov.  6 
Nov.  10 

Nov.  14 

Nov.  21 

Do... 

Nov.  28 
Nov.  29 


Character  of  she'.ier  and  food. 


Date  of 
last 
emer- 
gence. 


Weeds  and  pM  5  inches:  stalks  left . 
Weeds  and  grass  5  inches;  stalks 

removed    

Weeds  and  grass  4-o  inches;  stalks 

cut.  left  

Moss,  hark,  ehi]  s.  etc.;  no  food  

Orass  and  weeds  5  inches;  stalk) 

removed  

Stalks  pulled,  left:  grass  and  weeds 

5  inches  

Grass  and  weeds  10  inches;  stalks 

DOBsd  and  left    

\\  eeds  and  m  2  inches;  stalks 

pulled  and  left  

Ground  hare;  no  food  

Bolls  a  


1907. 
May  11 

May  15 

May  11 
June  15 

May  6 

Apr.  28 

May  23 


...do... 
Mav  11 
M  ir.  ! 


Total  and  average. 


Dumber 
of 

weevils. 


Total 
weevils 
emerged. 


2,375 

2,375 
2 .  s50 

2,850 

2,850 

2,850 

2.WI 
l.iiss 


201 
105 

134 

874 

3»i2 

449 

374 

RSK 
139 
2 


22,  U\3 


3,028 


Percent-    Rank  of 
aire  of    section  in 
survival,  survival. 


8.4<> 
4.42 


5.r,i 
23.  85 


12.  70 


13. 19 


20.  83 
12  78 


13.47 


a  Three  hushels  of  holls  on  the  surface,  and  3  bushels  covered  with  2  inches  of  earth. 

The  results  of  this  work  arc  exceptionally  striking  in  the  case  of  the 
Dallas  record.  The  ( 'al vert  record  ranges  between  that  of  Dallas  and 
Victoria  in  regard  to  the  clearness  with  which  comparative  effects  are 
shown.  In  each  case  there  is,  however,  a  general  tendency  toward 
more  successful  hibernation  as  the  season  advances  after  the  middle  of 
October  until  the  time  when  frosts  occur.  In  the  case  of  the  Dallas 
records  there  occurred  an  almost  uninterrupted  increase  in  percentage 
of  survival  with  each  date  upon  which  experiments  were  started. 
The  apparent  exceptions  are  readily  explainable  by  other  facts  than 
the  time  of  starting  the  experiment.  Section  12,  which  ranged  sixth, 
received  weevils  collected  at  Brownsville,  Tex.,  which  made  it  neces- 
sary to  ship  for  a  long  distance.  During  this  shipment  their  food 
supply  became  poor,  and  the  weevils  were  undoubtedly  much  weaker 

upon  being  placed  in  the  cage  than  were  those  which  had  been  col- 
lected in  the  immediate  vicinity  <»f  Dallas.  Section  (>  was  not  provided 
with  any  shelter  for  the  weevils,  and  the  percentage  of  survival  was 
smaller  on  that  account  than  in  other  sections  started  at  about  the 
same  date.  Section  10,  which  ranged  ninth,  received  only  infested 
bolls,  upon  and  within  which  weevils  were  hibernating.  From 
October  to  to  November  1o,  under  a pproximately  similar  conditions, 
the  percentage  of  survival  increased  from  2.61  to  31.34.  (See  PI. 
VTI,  figs.  2,  3.)  A  more  forceful  argument  than  this  for  the  destruc- 
tion of  the  food  supply  as  early  in  the  fall  as  is  possible  could  hardly 
be  given. 

A  combination  of  the  records  for  those  localities  at  which  experi- 
ments were  started  upon  the  same  or  approximate  dates,  grouping 
them  so  that  the  chronological  sequence  is  most  clearly  shown,  adds 
additional  emphasis  to  the  statements  which  have  just  been  made. 


76 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


Table  XXXVIII. — Comparison  of  sectional  records  grouped  by  approximate  initial 

dates. 


Date. 


1900. 
Oct.  13 

Do.... 
Oct.  1(5 


Oct.  19 
Oct.  20 


Oct.  24 
Oct.  25 

Do.... 

Do.... 


Oct.  28 
Oct.  30 
Oct.  31 


Nov.  5 
Do.... 
Nov.  G 


Nov.  10 
Nov.  12 
Nov.  14 
Nov.  13 
Nov.  14 
Nov.  15 


Nov.  21 
Do... 
Do... 


Nov.  25 
Nov.  20 
Nov.  28 
Do.... 


Locality. 


Dallas.. 
Calvert. 
Dallas.. 


Total  and  average. 


Calvert. 
Dallas.. 


Total  and  average. 


Dallas... 
Calvert. . 
Victoria. 
 do.. 


Total  and  average. 


Victoria. 
Dallas... 
Calvert.. 


Total  and  average 


Dallas... 
Calvert.. 
Victoria. 


Total  and  average. 


Victoria. 
Dallas... 
Calvert. . 
Dallas... 
Victoria. 
Dallas... 


Total  and  average. 


Dallas... 
Victoria. 
....do.. 


Total  and  average. 


Calvert. 
....do.. 


Dallas... 
Victoria. 


Total  and  average. 


Section 
number. 


Basis 
number 

of 
weevils. 


3,800 
2,375 
2,090 


8, 205 


2,375 
3,010 


5,  its;, 


3,325 
2,375 
2,375 
2,375 


10,450 


2, 3S9 
2,850 
2,375 


7,014 


3,135 
2,375 
2, 850 


8.360 


2, 850 
3,040 
2, 375 
3,040 
2,850 
2,505 


10,  720 


1,570 
2,  830 
2, 850 


7,250 


1,425 
1,358 
975 
1,088 


4,846 


Total 
number 
emerged. 


L16 

220 


Percent- 
age of 
survival. 


2.01 
3.15 
4. 07 


3.L 


4.  88 
6. 20 


231 
105 
201 
105 


042 


134 

250 
63 


45 
074 


1,102 


362 
448 
438 
788 
449 


65 
374 

588 


5.  71 


0.95 
4.42 
8.  40 
4.42 


0.15 


5.01 
8.85 
2.05 


5.  87 


12.  22 
1.89 
23. 05 


13. 18 


12.  70 

14.  74 
18.  44 
25.92 

15.  80 
31.34 


19. 67 


a  4. 14 
13. 19 

20. 03 


1,027 


b  14. 15 


359 
380 
40 
139 


924 


25.19 
27.  98 
c  4.  72 
12.  78 


d  19.  07 


Rank  in 
percent- 
age of 
survival. 


a  Brownsville,  Tex.,  weevils. 

b  Average  omitting  Brownsville  weevils,  10.91  per  cent. 

c  Absolutely  bare  ground. 

d  Average  without  Dallas  cage,  22.7  per  cent. 

In  this  table  it  may  be  seen  that,  taking  all  localities  together, 
whenever  experiments  were  started  upon  approximately  the  same 
date  there  is  a  most  striking  increase  in  successful  survival  at  inter- 
vals between  the  middle  of  October  and  the  middle  of  November. 
This  table  may  be  safely  considered  as  representing  in  the  most 
genera]  way  possible  the  facts  in  regard  to  this  point.  An  interval  of 
about  eleven  days  between  October  14  and  25  practically  doubled  the 
percentage  of  weevils  surviving.  Again,  in  an  interval  of  about  ten 
Hays  between  October  25  and  November  5  the  percentage  was  again 


EMERGENCE  FROM  HIBERNATION,  1907. 


77 


doubled,  and  an  increase  of  50  per  cent  was  observable  between 
November  5  and  14.  After  November  14  hibernation  might  have 
been  successful  for  practically  the  maximum  possible  proportion  of 
weevils.  The  relation  of  these  figures  may  be  most  simply  expressed 
in  the  following  manner:  Under  similar  conditions  of  shelter,  but 
without  a  food  supply,  if  the  survival  of  weevils  in  Texas  for  October 
15  is  one,  for  October  25  it  will  be  two;  for  November  5,  four;  and  for 
November  15,  six.  These  figures  make  it  evident  that  from  October 
15  to  November  15  constitutes  the  strategic  period  for  attack  upon  the 
boll  weevil.  The  attack  can  be  made  in  t  wo  ways :  (1)  By  the  destruc- 
tion or  removal  of  the  conditions  favorable  for  the  shelter  of  the 
weevil  through  the  winter;  (2)  by  the  destruction  of  the  food  supply. 
These  conclusions  have  frequently  been  stated  and  are  here  repented 
because  the  facts  here  presented  prove  more  conclusively  than  have 
any  other  data  heretofore  obtained  the  unquestionable  importance 
of  fall  work  in  combating  the  boll  weevil.  The  benefit,  obviously, 
will  always  be  realized  during  the  following  season  by  a  much  smaller 
injury  to  the  crop.  Considerations,  both  of  minimum  expense  and 
of  maximum  effectiveness,  emphasize  this  conclusion. 

SUBYIYAL  OF   WEEVILS   BY   LOCALITIES   AND  CAGE  SECTIONS. 

In  practically  all  of  the  sections  it  may  be  considered  that  the 
emergence  period  began  dining  the  last  few  days  of  February  and 
the  first  few  days  of  March,  March  1  being,  approximately,  the 
average  date  in  each  case.  In  the  following  table  the  summaries  of 
the  sectional  records  in  each  locality  are  given,  together  with  the  data 
necessary  to  show  the  maximum  length  of  tin1  hibernation  period  and 
the  percentage  of  survival  in  each  section: 

Tablk  \  X  X I X .    Maxim  a  in  hibernation  period  and  percentage  of  survival  by  sections, 

j  nor,. 

I  >  A  LLA8. 


Section  number. 


Total  and  avenge. 


When 

installed. 


1900. 
Oct.  13 
Oct.  20 
Nov.  12 
Oct.  10 
Nov.  5 
Nov.  2S 
Oct.  24 
Oct.  30 
Nov.  13 
Dec.  6 
Nov.  15 
Nov.  21 


Weevils 
started. 


3.S00 
3.200 
2,200 
3,300 
1,025 
3,500 
3,000 
3,200 
804 
2,700 
l.C..-)() 


32, 43!) 


Number 
used  as 
basis  of 
percent- 
age. 


a.  son 

3,010 
3,040 
2,090 
3,135 

975 
3,325 
2.  s50 
3,040 

804 
2,566 
1.570 


30, 804 


Date  of 
last 
emer- 
gence. 


1907. 
Mav  21 
May  19 
May  21 
Mav  ti 
Mav  15 
Apr.  29 
June  17 
June  15 
June  19 
May  2 
June  4 
June  8 


Total  Percent- 
weevils      age  of 
emerged,  survival. 


99 
22(5 
448 

85 
3S3 

40 
231 
250 
788 

39 
804 

05 


3,404 


78  HIBERNATION  OP  THE  COTTON  BOLL  WEEVIL. 


Table  XXXlX. — Maximum  hibernation  period  and  percentage  of  survival  by  sections , 

1 906— Continued. 

CALVERT. 


Section  number. 

When 
installed. 

Weevils 
started. 

Number 
used  as 
basis  of 
percent- 
age. 

Date  of 
last 
emer- 
gence. 

Total 
weevils 
emerged. 

Percent- 
age of 
survival. 

1  

1906. 
Oct.  13 
Nov.  26 
Nov.  14 
Oct.  19 
Nov.  5 
Nov.  25 
Oct.  25 
Oct.  31 
Nov.  12 
Dec.  3 

2, 500 
1,430 
2, 500 
2,500 
2,500 
1,500 
2, 500 
2.500 
2,500 
Bolls. 

2, 375 
1,358 
2,375 
2, 375 
2,  375 
1,425 
2, 375 
2, 375 
2, 375 
(a) 

1907. 
June  12 
....do.... 
May  31 
May  30 
Apr.  26 
May  16 
July  1 
May  30 
June  12 
Mar.  24 

75 
380 
253 
116 

45 
359 
105 

63 
438 
8 

■  3.15 
27. 98 
10.65 
4.  88 
1.89 
25.19 
4.  42 
2.65 
18.  44 

2  :  

3  

4  

5  

6  

8  :  

9  

10  

Total  and  average  

20, 430 

19, 408 

1,842 

9.49 

VICTORIA. 

1  

Oct  25 
Oct.  28 
Nov.  21 
Oct.  25 
Nov.  14 
Nov.  28 
Nov.  6 
Nov.  10 
Nov.  21 
Nov.  29 

2,500 
2,515 
3,000 
2,500 
3,000 
1,145 
3,000 
3,000 
2, 985 
(6) 

2, 375 
2, 389 
2,850 
2,  375 
2,  850 
1,088 
2, 850 
2,850 
2, 836 
(*) 

May  11 
....do.... 

May  23 
May  15 
Apr.  28 
May  11 
June  15 
May  (i 
May  23 
Mar.  4 

201 
134 
588 
105 
449 
139 
~674 
362 
374 
2 

8. 46 
5. 61 
20.  63 
4.42 
15.  86 
12.  78 
23.  65 
12.70 
13.19 

2  

3  

4  

5  

6  

8  

9  

10  

Total  and  average  

23, 645 

22, 463 

3,028 

13.  47 

a  No  estimate  made.        b  Three  bushels  of  bolls  on  surface  and  3  bushels  covered  with  earth. 


The  longest  period  of  hibernation  occurred  at  Calvert  among  the 
weevils  placed  in  section  7  on  October  25,  the  last  weevil  emerging 
from  this  section  being  taken  on  July  1,  1907.  During  this  period 
of  over  eight  months  this  weevil  survived  without  a  particle  of  food. 
This  may  be  considered  as  representing  the  maximum  hibernation 
period,  and  in  the  case  of  an  insect  producing  numerous  generations 
during  each  season  it  is  surprising  that  the  hibernation  period  can 
be  so  greatly  prolonged. 

The  largest  average  percentage  of  survival  occurred  at  Victoria, 
although  the  variation  between  the  three  localities  was  not  unex- 
pectedly great.  The  nature  of  the  shelter  provided  in  each  section 
has  been  indicated  upon  page  57.  A  comparison  of  the  records  for 
section  7  for  Calvert  and  Dallas  with  those  for  the  same  section  at 
Victoria  shows  that  at  the  last-named  place  the  survival  was  four 
times  as  great  as  in  the  average  of  Dallas  and  Calvert.  The  shelter 
provided  was  as  closely  similar  in  the  case  of  this  section  as  in  any 
of  the  series,  and  the  significant  point  of  difference  appears,  there- 
fore, to  be  the  time  when  weevils  were  inclosed.  At  Dallas  and  Cal- 
vert this  occurred  on  October  24  and  25,  respectively,  while  at 
Victoria  weevils  were  not  placed  in  the  cage  until  November  6. 
Apparently,  therefore,  the  much  larger  survival  at  Victoria  was  due 


EMERGENCE  FROM  HIBERNATION,  1907. 


79 


primarily  to  the  starting  of  the  experiment  about  twelve  days  later 
than  in  the  other  two  localities. 

The  significance  of  the  time  of  beginning  the  experiments  is  well 
emphasized  by  the  records  for  sections  2  and  6  at  Calvert.  These 
two  sections  furnished  by  far  the  highest  percentages  of  survival  at 
that  place,  and  apparently  the  only  fact  explaining  this  is  that  the 
experiment  was  started  in  each  case  at  the  time  which  was  most 
favorable  for  successful  hibernation,  i.  e.,  about  November  25.  This 
date  was  ten  or  twelve  days  later  than  those  for  sections  3  and  9, 
which  present  the  next  higher  percentages  of  survival.  An  average 
of  these  two  sections  shows  that  among  the  weevils  starting  hiber- 
nation about  November  12.  14.r>  per  cent  survived,  while  among 
those  starting  hibernation  about  November  25,  about  26.5  per  cent 
survived. 

The  records  for  Dallas  show  that  the  three  highest  percentages  of 
survival  occurred  in  sections  LI,  '.».  and  which  were  started  between 
November  1 2  ami  l .">. 

In  each  locality  the  average  date  for  the  termination  of  emergence 
occurred  between   May  22  and  2D.     It   is  evident,  therefore,  that 

during  !*>()()  the  period  of  emergence  From  hibernation  covered 
practically  three  months  for  an  average  of  all  of  the  sections  and 

slightly  more  than  four  1 1 i < > i i t lis  for  the  last  emerged  weevils. 

MONTHLY   SUMMARY   OF   EMERGENCE  RECORDS. 

While  it  is  important  to  know,  approximately  at  least,  the  maxi- 
mum limit  of  the  emergence  period,  it  may  seem  more  desirable  to 
determine  the  time  at  which  a  majority  of  weevils  surviving  had 
emerged.  It  is  more  convenient  in  using  the  records  to  compare 
them  in  four-week  periods  rather  than  according  to  calendar  months. 


Table  XL.  —  Enurycna'  in  I'm:,  by  four-mrk  periods. 


I  ocality. 

Mar.  1-28,  wee- 

\  iis  emerged. 

Mar.  29-Apr  26,  Apr.  20-May  23, 
\vee\  i  Is  emerged,  weevils  emerged. 

May  21-July  I, 

ireevils  emerged. 

Total 
emer- 
gence. 

Num- 
ber. 

rer 

(•('111  (if 

total. 

Num- 
ber. 

l'cr 
cent  of 
total. 

Num- 
ber. 

Per 

ccnl  of 
total. 

Num- 
ber. 

Tor 
cent  of 
total. 

Dallas  

Calved  

Victoria  

Total  and  average  

2, 4S6 
1,053 
2,399 

71. S 
571 

79.3 

4S4 
410 

476 

14.0 
22.  3 
15.7 

452 
284 
119 

13  0 
15.4 
3.9 

42 

95 
32 

1.2 

5.2 

3,  464 
1 .  B  l_> 

3,026 

5,938 

71.3 

1,370 

164 

855 

10.3 

169 

2.0 

8,332 

WEEKLY    K.MEHCKNCK  RECORDS. 

The  following  table  presents  a  summary  of  the  daily  emergence 
records  for  each  section  during  seven-day  periods  from  March  1  to  the 
end  of  the  hibernation  period.    These  records  are  particularly  inter- 


80  HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 

esting  in  showing  the  variation  occurring  in  emergence  in  the  same 
section  and  locality  during  the  different  periods. 

Table  XLI. — Summary  of  emergence  of  iveevils  in  cage  sections  by  weekly  periods, 

March  1  to  June  20,  1907. 

DALLAS. 


Weekly  period. 


Mar.  1-7  

Mar.  8-14  

Mar.  15-21  

Mar.  22-28  

Mar.  29- Apr.  4. 

Apr.  5-11  

Apr.  12-18  

Apr.  19-25  

Apr.  26-Mav  2 . 

May  3-9  

May  10-16  

May  17-23  

Mav  24-30  

May  31-June  6. 

June  7-13  

June  14-20  


Number  of  weevils  emerged  in  section  number- 


Total. 


1. 

2. 

3. 

4 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

40 

69 

155 

36 

151 

21 

73 

79 

212 

12 

8 

36 

51 

10 

46 

7 

25 

31 

120 

7 

65 

7 

17 

39 

85 

11 

89 

11 

64 

35 

202 

13 

145 

10 

10 

21 

38 

8 

51 

2 

25 

22 

123 

4 

189 

11 

4 

20 

19 

3 

8 

1 

4 

15 

7 

1 

49 

4 

7 

13 

30 

7 

10 

3 

7 

10 

17 

1 

78 

11 

1 

6 

12 

1 

7 

0 

8 

5 

10 

0 

55 

6 

1 

5 

8 

0 

1 

0 

2 

3 

6 

0 

15 

0 

5 

10 

16 

3 

5 

1 

2 

20 

8 

1 

27 

1 

2 

3 

21 

3 

7 

0 

7 

14 

26 

0 

40 

6 

2 

2 

10 

0 

8 

0 

2 

7 

29 

0 

58 

3 

2 

2 

3 

0 

0 

0 

8 

3 

16 

0 

67 

2 

0 

0 

0 

0 

0 

0 

0 

3 

4 

0 

12 

1 

0 

0 

0 

0 

0 

0 

1 

2 

4 

0 

4 

2 

0 

0 

0 

0 

0 

0 

1 

0 

3 

0 

0 

1 

2 

1 

1 

99 

226 

448 

82 

383 

46 

231 

250 

788 

39 

804 

65 

CALVERT. 


Mar.  4-7  

Mar.  8-14  

Mar.  15-21  

Mar.  22-28  

Mar.  29-Apr.  4. 

Apr.  5-11  

Apr.  12-18  

Apr.  19-25  

Apr.  26-Mav  2. 

Mav  3-9  

Mav  10-16  

May  17-23  

May  24-30  

May  31-June  6. 

June  7-13  

June  14-20  

June  21-27  

June  28-July  4 . 


25 


Total. 


136 
47 
45 
57 
22 
L'l 
16 
6 
3 
3 
3 
0 
0 
0 
0 
0 


75      380      253      116       45      359      105       63  I  438 


VICTORIA. 


Feb.  28  

39 

24 

23 
36 
18 
10 
6 

69 

13 
20 
22 
19 
13 
9 

60 

35 
29 
24 
25 
18 
5 

29 

31 
92 
107 
72 
26 
15 
8 
5 

63 
72 
76 
67 
30 
16 
12 
25 
6 

Mar.  1-7  

32 

95 
130 
94 
54 
51 
44 
28 
9 

80 
103 

.  88 

36 

2 

Mar.  8-14  

54 

63 

0 

Mar.  15-21  

36 
18 
9 

124 
170 
19 
64 
47 
11 
14 
31 
20 
14 
8 
21 
2 

0 

Mar.  22-28  

58 
17 
26 
7 

0 

0 

Mar.  29-Apr.  4  

Apr.  .5-11  

3 

8 

0 

0 

n  i 

Apr.  12-18  

5 

5 

5 

0 

0 

Apr.  19-25  

Apr.  26-Mav  2  

! 

2 

1 

0 
2 

1 
1 

0 

6 

0 

2 

0 

4 

4 

0 

1 
4 

0 

Mav  3-9  

8 

0 

0 

3 

0 

May  10-16  

1 

1 

0 

1 
1 

0 
0 
0 

2 

0 

1 

0 

0 

0 
2 

0 

0 

0 

0 

0 

0 

May  24-30  

0 

0 

0 

0 

0 

0 

0 

0 

May  31-June  6  

0 

0 

0 

0 

0 

0 
0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

June  14-20  

1 

Total  

201 

134 

588 

105 

119 

137 

674 

362 

374 

2 

EMERGENCE  FROM  HIBERNATION,  1907. 


81 


There  is  no  indication  that  the  time  at  which  an  experiment  was 
begun  affected  essentially  the  nature  of  the  emergence  movement. 
The  nature  of  the  shelter,  however,  does  seem  to  have  an  important 
influence.  This  is  most  clearly  marked  in  section  7,  where  the  ex- 
perimental shelter  was  Spanish  moss.  At  Victoria  after  about  the 
12th  of  April  more  weevils  emerged  from  this  section  than  from  all 
others  combined.  This  effect  was  less  marked  in  the  other  localities, 
but  in  each  case  there  appeared  to  be  a  considerable  delay  in  emer- 
gence, due  to  the  nature  of  this  shelter.  Owing  to  the  fact  that  this 
moss  is  living  and  growing  while  hanging  CD  the  cages  or  on  the  trees, 
it  takes  up  moisture  as  no  other  class  of  shelter  does.  The  evapo- 
ration of  this  moisture  during  the  daytime  then  serves  to  keep  the 
mass  of  moss  cool,  and  it  is  a  well-known  fact  that  the  temperature 
in  bunches  of  this  moss  is  several  degrees  lower  than  that  of  the  air 
during  the  daytime.  Undoubtedly  the  lower  temperature  in  the 
moss  is  the  factor  which  retards  the  emergence  of  the  weevils  so 
decidedly.  This  factor  may  also  he  considered  responsible  for  the 
smaller  activity  of  weevils  shown  in  the  moss  sections  during  the 
winter.     (See  Table  XXXI.  p.  (13.) 

A  somewhat  more  detailed  statement  of  the  emergence  shows  more 
plainly  the  peculiar  manner  in  which  this  was  distributed  during 
1907.  The  figures  an*  arranged  for  seven-day  periods,  and  show  the 
average  temperature  conditions  prevailing  as  we]]  as  the  percentage 
total  of  emergence  occurring  during  each  week. 

TABLE  XL1I. —  Wnlch/  su  m  indrij  of  rnun/iiirr  r»  mn/s,  shturinij  nhitimi  to  rjj'i  ct  i  rr  trm- 

peratuns,  1U<>7. 


a  On  February  28. 


Vrvi'ui- 
age  of 
total 
emer- 


90317— Bull. 


-09- 


82 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


Table  XLII. — Weekly  summary  of  emergence  records,  showing  relation  to  effective  tem- 
peratures, 1907 — Continued. 


Mean 
average 
effective 
tempera- 
ture. 

Number 
of  weevils 
emerged. 

Percent- 
age of 
total 
emer- 
gence. 

°F. 

26.4 

113 

6.1 

20.2 

129 

3.7 

29.3 

50 

1.6 

31.9 

59 

3.2 

24.0 

121 

3.5 

32.5 

26 

.86 

35.5 

54 

3.0 

31.2 

103 

3.0 

31.8 

17 

.50 

33.0 

49 

2.6 

23.3 

20 

.6 

33.4 

8 

.26 

30.7 

30 

1.6 

38.0 

13 

.4 

30.9 

21 

43.2 

10 

:i 

38.0 

5 

40.0 

2 

37.4 

5 

.3 

36.0 

4 

.12 

36.8 

1 

.03 

39.4 

1 

.01 

Date. 


1907. 


May  3- 


May  10-1C) 


May  17-2.1 


May  24-30. 


May  31-June  6. 


June  7-13. 


June  14-20. 


Locality. 


June  21-27 


(Calvert.. 
\  Dallas... 
(Victoria. 
(Calvert.. 
\  Dallas... 
I  Victoria. 
(Calvert.. 
\  Dallas... 
(Victoria. 
I  Calvert.. 
{Dallas... 
[Victoria. 

Calvert.. 
\  Dallas... 
(Victoria. 

Calvert.. 
{Dallas... 
(Victoria. 

Calvert.. 
{Dallas... 
(Victoria. 

Calvert.. 

Dallas... 

Victoria. 


Total  emergence: 

Calvert   1,842 

Dallas  3,464 


Victoria  

Grand  total. 


3,026 
8,332 


The  large  percentage  of  total  emergence  occurring  during  the  first 
week  of  March  is  very  striking  and  unquestionably  also  very  excep- 
tional. Only  the  extremely  high  range  in  temperature  can  explain 
this  unusual  record.  Taking  the  average  of  the  three  locations, 
practically  one-fourth  of  the  total  emergence  occurred  during  the 
first  week  of  March.  During  the  following  two  weeks  more  than 
another  one-fourth  also  emerged.  During  this  period  the  tempera- 
tures averaged  as  high  as  they  do  ordinarily  in  May;  and  owing  to 
the  fact  that  a  considerable  majority  of  weevils  had  left  shelter 
before  the  end  of  March  the  number  emerging  after  that  time  shows 
a  marked  decrease. 

It  must  not  be  supposed  that  these  statements  represent  anything 
like  usual  conditions,  although  they  unquestionably  represent  the 
facts  in  regard  to  emergence  in  1907.  The  comparison  of  these 
records  with  those  for  Dallas  and  Keatchie  (see  p.  44)  in  1906  will 
show  clearly  the  exceptional  nature  of  the  variation. 

It  should  be  stated  that  when  the  emergence  takes  place  as  rapidly 
as  w  as  the  case  in  March,  1907,  the  actual  number  of  living  weevils 
in  t  he  field  may  be  expected  to  increase  for  some  time  because  of  the 
fact  that  a  larger  number  of  weevils  is  added  to  the  total  living  on 
account  of  continued  emergence  than  is  lost  on  account  of  death 
among  weevils  which  have  previously  emerged. 


LONGEVITY  OF   WKKVILS  AFT K II   KM  KliCKXCE. 


83 


LONGEVITY     OF    WEEVILS     AFTER    EMERGENCE  FROM 
HIBERNATION. 

Preceding  records  have  shown  that  on  the  average  the  weevils  sur- 
viving hibernation  had  lived  for  over  five  months  before  their  emer- 
gence.  It  is  impossible  to  determine  even  approximately  how  old 
weevils  may  have  been  at  the  time  they  were  placed  in  the  hiberna- 
tion cages.  The  longevity  records  here  shown  must ,  therefore,  be 
very  conservative.  They  may  indicate  veiy  closely  the  average 
Length  of  lifeof  weevils  which  survive  hibernation,  but  should  not  be 
considered  as  showing  actually  the  maximum  longevity.  It  has 
seemed  advisable,  therefore,  to  base  the  studies  upon  longevity  after 
emergence  from  hibernation,  since  the  exact  dates  for  emergence  and 
for  deaths  have  been  carefully  determined. 

A.s  the  weevils  were  collected  daily  from  the  cages,  those  found  at 
each  date  must  have  emerged  practically  upon  that  date.  It  was 
the  general  practice  to  divide  the  weevils  from  each  section  of  the 
cage  into  two  lots  of  approximately  equal  numbers,  one  lot  being 
placed  in  a  series  in  which  they  received  DO  food  and  the  second  lot 
being  placed  in  a  series  which  was  supplied  whatever  stage  of  cotton 
was  then  available  to  weevils  in  the  field  where  the  experiments  were 
being  made.  Thus,  early  in  the  season  at  Dallas,  all  weevils  were 
necessarily  placed  in  unfed  series,  since  no  cotton  existed  in  the  field. 
In  each  locality  the  first  food  consisted  of  t  he  tender  leaves  of  volun- 
teer or  sprout  plants.  As  soon  as  squares  were  formed  in  the  held 
these  were  supplied  to  the  weevils  in  the  fed  series  of  experiments. 

As  a  general  rule  the  weevils  emerging  upon  three  consecutive 
days  were  placed  in  a  cage  bearing  the  same  series  designation,  and 

the  average  date  of  emergence  was  considered  as  applying  to  the 

entire  lot.  This  arrangement  was  necessary  to  reduce  the  amount  of 
work  required  in  caring  for  so  many  cages  as  would  be  needed  to 
keep  each  day's  weevils  entirely  separate. 

In  both  the  fed  and  unfed  series  frequent  examinations  were  made 
to  determine  the  time  of  death  of  each  weevil,  and  fresh  food  was 
supplied  to  weevils  in  the  fed  series.  Upon  the  death  of  a  weevil 
its  sex  was  determined  and  its  period  of  life  after  emergence  was  also 
recorded.  The  manner  in  which  sex  can  be  positively  determined  is 
described  in  succeeding  paragraphs.  (See  p.  91.)  In  this  way  the 
records  for  each  lot  bearing  a  serial  number  were  kept  by  themselves 
and  the  results  for  each  series  are  comparable  with  all  others.  While 
it  would  be  most  significant  to  present  the  records  in  the  form  of  a 
summary  of  each  series  which  would  allow  these  comparisons  to  be 
seen,  the  necessity  for  abridging  the  tabular  matter,  so  far  as  may  be 
possible,  prevents  our  doing  so.  Therefore  for  both  the  " unfed" 
and  for  the  "fed"  experiments  we  can  give  only  the  grand  totals 
and  averages  with  general  statements  based  upon  the  tabular  studies 
from  which  these  figures  are  obtained. 


84 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


LONGEVITY  OF  US  FED  WEEVILS  AFTER  EMERGENCE  FROM  HIBERNATION. 

Since  the  duration  of  life  of  unfed  weevils  was  so  much  shorter 
than  for  fed  weevils,  the  records  of  the  former  will  be  considered 
first.  The  principal  object  in  the  experiments  with  unfed  weevils 
was  to  determine  the  time  which  they  might  survive  while  waiting 
for  the  growth  of  a  food  supply  in  the  spring.  The  results  have  a 
most  important  special  bearing  upon  the  advisability  of  hastening 
or  deferring  the  time  of  planting  of  cotton,  especially  when  considered 
in  connection  with  the  period  of  emergence  from  hibernation.  The 
figures  given  are  based  upon  completed  records  only,  all  partial 
records  having  been  discarded. 


Table  XLIII. — Longevity  of  unfed  weevils  after  emergence  from  hibernation,  March 

to  July,  1907. 


Locality. 

Number 
of  series 
tested 
unfed. 

Total 
weevils 
emerged. 

Weevils  in  series  lots. 

Maximum  life. 

Average  duration  of  life. 

Total. 

3 

? 

6 

2 

3 

2 

Both 

sexes. 

Texas: 

Calvert  

Dallas  

Victoria  

Total  and 
average . 

25 
19 
17 

1,085 
2,317 
1,418 

1,079 
2,179 
1,360 

585 
1,178 
875 

494 
1,009 
485 

Days. 
48 
90 
44 

Days. 
26 
88 
40 

Days. 
8.05 
13.  00 
8.  00 

Days. 
8.09 
11.09 
7. 40 

Days. 
8. 07 
12.50 
8. 20 

61 

4,820 

4,618 

'2,638 

1,988 

90 

88 

10.  30 

9.80 

10. 10 

The  records  both  for  maximum  and  average  duration  of  life  are  very 
important.  In  the  record  showing  maximum  and  average  duration 
of  life  for  each  sex  in  each  locality  the  time  at  Dallas  exceeds  by  50 
per  cent  the  time  at  either  Calvert  or  Victoria.  It  should  be  stated 
that  when  weevils  are  kept  in  confinement  it  is  probable  that  the  most 
favorable  conditions  which  can  be  furnished  them  can  hardly  be  sup- 
posed to  prolong  their  life  beyond  the  normal  condition  in  the  field. 
Any  unfavorable  conditions  in  the  cages  will  shorten  the  period.  It 
was  found  in  the  course  of  the  work  that  whenever  sunshine  was 
allowed  to  strike  directly  on  the  lantern  globe  breeding  jars  in  which 
the  weevils  were  for  the  most  part  confined,  the  heat  and  excessive 
humidity  generated  within  the  globe  caused  an  abnormal  activity 
among  the  weevils,  and  if  prolonged  or  frequently  repeated,  it 
resulted  in  their  early  death.  It  was  also  found  that  in  the  breeding 
cages  among  the  unfed  weevils  the  degree  of  moisture  was  less  than 
would  normally  occur  on  plants  or  at  the  surface  of  the  ground  in  the 
field.  This  dryness  also  naturally  shortens  the  life  of  weevils.  In 
an  experiment  at  Dallas  series  14  was  kept  with  plenty  of  moisture 
while  series  15  was  dry.  Otherwise  conditions  in  the  two  series  were 
identical.  The  average  life  in  the  wret  series  was  20.3  days  while  in 
I  he  dry  scries  it  was  but  7.1  days.  Other  experiments  pointed  to  the 
same  conclusion. 


LONGEVITY  OF  WEEVILS  AFTER  EMERGENCE. 


85 


Those  facts  indicate  that  the  records  for  Calvert  and  Victoria  are 
probably  considerably  below  the  normal  survival  period  for  emerged 
weevils  in  the  field,  and  the  records  for  Dallas  are  at  least  conserva- 
tive. The  difference  in  duration  of  life  between  the  males  and 
females  was  but  slight,  but  rather  uniformly  in  favor  of  the  males. 
In  each  locality  the  maximum  longevity  was  shown  by  males.  This 
fact  agrees  with  previous  conclusions  regarding  the  relative  duration 
of  life  of  the  two  sexes.  Apparently  copulation  does  not  materially 
affect  the  longevity  of  either  sex.  In  this  connection  it  may  be 
stated  that  unquestionable  instances  of  mating  were  found  among 
weevils  immediately  after  their  emergence  and  before  there  was  any 
possibility  of  their  having  fed.  This  was  of  rare  occurrence,  and  the 
question  of  fertility  resulting  was  not  positively  determined. 

From  the  records  it  becomes  evident  that  many  emerged  weevils 
may  survive  from  six  to  twelve  weeks  without  food  and  that  the 
average  survival  for  all  weevils  may  be  between  one  and  two  weeks. 

There  iv  some  evidence  to  show  that  it  is  possible  for  these  unfed 
weevils  to  move  rather  extensively  in  search  of  food,  and  undoubtedly 
this  is  done  in  many  instances.  Other  observat  ions,  however,  indi- 
cate that  if  food  is  not  found  in  the  vicinity  of  emergence  the  weevils 
may  become  quiet  for  a  considerable  period  before  again  seeking  food, 
and  in  this  way  their  movement  may  occur  only  through  compara- 
tively short  distances.  It  is  also  probable  that  when  they  first  find 
a  food  supply  they  do  not  intentionally  Leave  it  LD  search  of  other 
plants  which  may  be  in  a  more  advanced  stage  of  growth. 

As  to  the  proportion  of  each  sex  among  the  weevils  surviving  in 
these  experiments  it  appears  that  57  percent  were  males.  The  maxi- 
mum longevity  of  any  weevil  was  ninety  days.  This  was  a  male 
which  was  kept  under  outdoor  conditions  from  March  1,  when  it 
emerged,  to  May  .'!(),  when  it  died.  The  maximum  life  for  a  female 
was  eighty-eight  days.  This  weevil  emerged  April  25  and  died  July 
20.  The  average  temperature  under  which  this  lot  of  weevils  was 
kept  ranged  between  15  and  60  degrees  and  the  average  length  of  life 
for  all  of  the  55  weevils  tested  in  series  17  at  Dallas  w  as  slightly  more 
than  thirty  days.  This  emphasized  the  important  etl'ect  of  tempera- 
ture upon  the  period  of  survival  without  food. 

The  grand  total  for  average  duration  of  life  shows  10.1  days  for 
more  than  4,600  weevils.  The  males  lived  on  an  average  one-half 
day  longer  than  did  the  females. 

It  would  be  both  interesting  and  valuable  if  the  records  showing  a 
summary  of  the  results  for  each  sex  in  each  series  of  experiments 
could  be  presented  in  full.  It  is  thought,  however,  that  the  corre- 
sponding records  for  the  fed  weevils  have  a  greater  value  and  it  may 
be  allowable  to  present  in  place  of  the  full  records  for  the  unfed 
weevils  merely  a  brief  statement  of  the  most  important  facts  as  to 
the  survival  of  each  sex. 


86 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


The  most  apparent  fact  is  that  there  is  a  consistent  increase  in 
duration  of  life  without  food  in  both  sexes  in  a  northern  locality,  as 
at  Dallas,  as  compared  with  a  southern  locality,  as  at  Victoria,  while 
Calvert  occupies  an  intermediate  position  both  in  the  starvation 
period  and  geographically.  Lower  temperatures  are  obviously  directly 
correlated  to  the  degree  of  activity  of  the  insects  and  thus  determine 
directly  the  limit  of  endurance  without  food.  But  in  no  case  is  there 
any  very  marked  variation  between  the  sexes  in  the  same  locality. 

It  appears  that  practically  two-thirds  of  all  weevils  died  during 
the  first  ten  daA^s  after  their  emergence.  One-fourth  of  the  total  num- 
ber tested  lived  to  between  eleven  and  twenty  days.  Beyond  twenty 
days  the  percentage  surviving  becomes  comparatively  small,  and 
between  fifty  and  ninety  days  the  percentage  for  each  ten-day 
period  is  rather  surprisingly  uniform.  It  is  very  evident,  however, 
that  even  in  a  season  when  the  bulk  of  emergence  may  occur  as 
unusually  early  as  it  did  in  1907  it  would  be  absolutely  impossible 
to  exterminate  the  weevil  by  any  possible  delay  in  the  time  of  plant- 
ing cotton. 

LONGEVITY  OF  FED  WEEVILS  AFTER  EMERGENCE  FROM  HIBER- 
NATION. 

The  records  indicating  the  longevity  of  weevils  which  were  fed 
after  their  emergence  from  hibernation  have  been  prepared  in  a 
similar  way  to  show  results  comparable  with  those  for  unfed  weevils 
which  have  just  been  given.  They  form  the  second  part  of  the  com- 
parative series  of  experiments  to  determine  longevity.  The  condi- 
tions of  food  supply,  while  kept  as  favorable  as  was  possible,  could 
not  at  best  equal  the  natural  conditions  in  the  field,  although  the 
weevils  were  evidently  saved  the  trouble  which  they  might  have 
experienced  in  the  field  of  finding  their  first  food  supply.  The  con- 
siderations which  have  previously  been  mentioned  in  regard  to  the 
effect  of  high  temperature4  and  excessive  moisture  in  the  jars  when 
exposed  to  sunshine  apply  with  fully  as  much  force  to  the  fed  as  to 
the  unfed  series  of  experiments. 


Table  XLIV. — Longevity  of  weevils  fed  after  emergence  from  hibernation,  March  to 

September,  1907. 


Locality. 

Number 
of  series 
tested, 
fed. 

Total 
weevils 
emerged. 

Number  of  weevils  in 
series. 

Maximum  life. 

Average  duration  of  life. 

Total. 

9 

9 

e 

9 

Both 
sexes. 

Texas: 

Dallas  

Calvert  

Victoria 

Total  and 
average . 

7 
20 
20 

998 
740 
1,450 

901 
715 
1,349 

490 
363 
785 

in 

352 
564 

130 
92 
M 

108 
118 

86 

38.4 
29.2 
15. 1 

38.0 
30.7 
14.2 

38.2 
30.0 
14.7 

53 

3, 188 

2,965 

1,638 

1,327 

130 

118 

25.2 

25.9 

25.5 

LONGEVITY  OF  WEEVILS  AFTER  EMERGENT!  . 


87 


Only  about  two-thirds  as  many  weevils  were  carried  through  in 
the  fed  tests  as  in  the  unfed  tests.  Anionic  the  total  of  2,965  weevils 
56  per  cent  were  males,  while  in  the  unfed  experiments  57  per  cent 
were  males.  The  average  duration  of  life  shows  but  very  slight 
variation  between  the  sexes,  both  living  between  twenty-five  and 
twenty-six  days.  This  average  is  somewhat  smaller  than  has  pre- 
viously been  obtained  in  similar  experiments,  and  this  is  probably 
due  to  the  greater  exposure  to  sunshine  of  the  cages  in  which  the  wee- 
vils were  kept  in  this  series  of  experiments.  The  average  period  of 
life  with  food  was  about  two  and  one-half  times  that  without  food. 

Among  the  fed  weevils,  as  among  the  unfed,  the  longest  life  occurred 
at  Dallas.  This  also  was  a  male  weevil  which  emerged  from  hiberna- 
tion on  May  6  and  survived  until  September  13,  or  one  hundred  and 
thirty  day-.  The  greatest  length  of  life  for  a  female  occurred  at  Cal- 
vert. This  weevil  emerged  on  April  1  1  and  died  on  August  7.  having 
been  active  one  hundred  and  eighteen  days. 

The  full  length  of  life  of  the  last  weevil  dying  in  these  experiments 
is  also  a  matter  of  interest.  'Phis  weevil  was  collected  in  the  Held  at 
Dallas  and  placed  in  the  hibernation  cage  on  October  IT),  1906. 
From  that  time  until  May  (i.  L907,  it  had  no  food.  The  period  from 
its  collection  until  its  death  lacked  but  a  day  or  two  of  being  eleven 
months,  during  three-fifthfl  of  which  period  it  existed  without  food. 
This  is  next  to  the  longest  lived  boll  weevil  of  which  we  have  record, 
the  longer  record  being  slight lv  more  than  eleven  months  in  the  case 
of  a  male  weevil  hibernated  at  Victoria  in  1903. 

In  a  study  of  the  emergence  movement  and  of  the  duration  of  life 
of  fed  weevils  by  ten-day  periods  we  have  used  the  total  number  of 
Weevils  of  each  sex  observed  in  each  locality  as  the  basis  upon  which  we 
have  determined  the  percentage  of  mortality  occurring  in  each  succes- 
sive ten-day  period.  The  full  records  for  each  locality  have  been 
omitted  and  only  the  totals  for  each  sex  in  each  locality  have  been 
included  in  Table  XL V  (p.SS).  The  emergence  from  hibernation  was 
distributed  through  four  months,  or  slightly  more,  in  1907.  A  study 
of  tin  omitted  records  shows  that,  as  a  rule,  tin"  weevils  living  longest 
emerged  at  approximately  the  middle  of  the  emergence  movement. 
It  is  probable  that  these  weevils  were  among  those  which  entered 
hibernation  at  the  most  favorable  period  during  the  preceding  fall 
and  that  they  found  also  the  most  favorable  class  of  shelter  conditions 
to  protect  them  during  the  winter.  The  importance  of  breaking  up 
this  succession  of  conditions,  so  favorable  to  the  survival  of  weevils, 
their  maximum  length  of  life,  and,  consequently,  their  greatest  inju- 
riousness,  need  only  be  mentioned  to  be  appreciated.  That  early 
fall  destruction  of  stalks,  the  cleaning  up  of  rubbish  which  might 
shelter  weevils  most  favorably  during  the  winter,  and  the  early 
planting  and  uniform  planting  of  the  crop  are  all  logical  parts  or  steps 


88  HIBEKNATION  OF  THE  COTTON  BOLL  WEEVIL. 

in  the  rational  method  of  fighting  the  boll  weevil  is  plainly  shown  by 
these  studies. 


Table  XLV. — Comparison  of  summaries  for  longevity  of  fed  weevils,  by  ten-day  periods, 

in  each  locality. 

MALE  WEEVILS. 


Locality. 

Number 
of  weevils 
in  series. 

Weevils  dying  within  a  period  of— 

1-10  days. 

11-20  days. 

21-30  days. 

31-40  days. 

41-50  days. 

51-60  days. 

Num- 
ber. 

Per 
cent. 

Num- 
ber. 

Per 
cent. 

Num- 
ber. 

Per 
cent. 

Num- 
ber. 

Per 
cent. 

Num- 
ber. 

Per 
cent. 

Num- 
ber. 

Per 
cent. 

Dallas  

Calvert  

Victoria  

Total  and 
average . 

490 
363 
785 

47 

80 
371 

9.6 
23.8 
47.3 

72 
61 
216 

14.7 
16.9 
27.6 

87 
60 
116 

17.7 
16.7 
14.8 

68 
50 
39 

13.9 
13.8 
5.0 

87 
49 
14 

17.7 
13.5 
1.8 

47 
41 
13 

9.6 
11.3 
1.7 

1,638 

504 

30.2 

349 

21.3 

263 

16.0 

157 

9.6 

150 

9.2 

101 

6.2 

FEMALE  WEEVILS. 

Dallas  

Calvert  

Victoria  

Total  and 
average . 

411 

352 
564 

32 
67 
293 

7.8 
18.8 
51.9 

54 
63 
133 

13.1 
17.7 
23.5 

91 
60 
88 

22.1 
16.7 
15.6 

46 
58 
24 

11.2 
16.3 
4.3 

91 
54 
11 

22.1 
15.2 
2.0 

37 
32 
10 

9.0 
9.0 
1.8 

1,327 

392 

29.5 

250 

18.8 

239 

18.0 

128 

9.6 

156 

11.7 

79 

5.9 

WEEVILS  OF  BOTH  SEXES. 


Total  and  average,  2,967  

896  30.2 

599 

20.2 

502 

16.9 

285 

9.6 

306 

10.3 

180 

6.1 

MALE  WEEVILS. 


Weevils  dying  within  a  period  of— 

Locality. 

Number 
of  weevils 

61-70 

days. 

71-80 

days. 

81-90 

days. 

91-100 

days. 

Over  100 
days. 

in  series. 

Num- 

Per 

Num- 

Per 

Num- 

Per 

Num- 

Per 

Num- 

Per 

ber. 

cent. 

ber. 

cent. 

ber. 

cent. 

ber. 

cent. 

ber. 

cent. 

Dallas  

490 

36 

7.3 

31 

6.3 

5 

1.0 

7 

1.5 

2 

0.4 

Calvert  

363 

7 

1.9 

6 

1.7 

2 

1.6 

2 

.6 

0 

Victoria  

785 

4 

.5 

8 

1.0 

3 

.4 

0 

Total  and 

average . 

1,638 

47 

2.9 

45 

2.8 

10 

.6 

9 

.6 

2 

.1 

FEMALE  WEEVILS. 

Dallas  

411 

32 

7.8 

22 

5.4 

4 

1.0 

1 

0.2 

1 

0.2 

Calvert  

352 

9 

2.5 

3 

.8 

5 

1.4 

2 

.6 

1- 

.3 

Victoria  

564 

4 

.7 

.2 

1 

.2 

0 

0 

Total  and 

average . 

1,327 

45 

3.4 

26 

2.0 

10 

.8 

3 

.2 

2 

.1 

WEEVILS  OF  BOTH  SEXES. 


92 

3.1 

71 

2.4 

20 

0.7 

12 

0.4 

4 

LONGEVITY  OF  WEEVILS  AFTER  EMERGENCE. 


89 


At  Dallas  the  number  of  weevils  surviving  for  two  months  or 
more  amounted  to  15.6  per  cent  of  the  total  number  observed.  Prac- 
tically 50  per  cent  of  each  sex  survived  for  more  than  six  weeks. 

At  Calvert  15  per  cent  of  the  total  number  of  weevils  survived 
over  fifty  days  and  50  per  cent  for  more  than  thirty  days.  The 
average  life  at  Calvert  was  nearly  ten  days  less  than  at  Dallas.  It 
is  very  noticeable  that  those  weevils  which  lived  longest  at  Calvert 
emerged  during  about  the  middle  of  the  emergence  period.  The 
weevils  which  were  very  late  in  emerging  survived  for  only  a  short 
time.  The  decrease  in  the  percentage  of  survival  is  markedly  regular 
from  the  first  ten  days  to  the  end  of  the  period.  The  most  decided 
decrease  occurs  between  sixty  and  seventy  days. 

The  maximum  longevity  at  Victoria  fell  considerably  short  of 
that  at  Calvert  and  Dallas.  In  this  case  15  per  cent  of  the  weevils 
survived  beyond  only  about  twenty-live  days  and  nearly  50  per 
cent  died  during  the  first  ten  days.  The  reason  for  the  marked 
shortening  of  life  at  Victoria  was  undoubtedly  the  greater  exposure 
to  sunshine  of  the  jars  in  which  the  weevils  were  confined. 

This  comparison  shows  that  length  of  life  uniformly  averages 
longer  in  northern  Texas  than  in  either  central  or  southern  Texas. 
At  Dallas  .'J  weevils,  at  Calvert  1.  and  at  Victoria  none  lived  more 
than  one  hundred  days.  At  Dallas  11  weevils,  at  Calvert  5,  and  at 
Victoria  none  lived  more  than  ninety  days.  From  the  grand  sum- 
mary of  the  records  in  both  sexes  it  appears  that  among  approxi- 
mately 3,000  weevils  50  per  cent  died  dining  the  first  twenty  days. 
Two-thirds  of  them  died  in  the  first  thirty  days  and  three-fourths  of 
them  in  the  first  forty  days. 

From  these  records  it  appears  that  any  kind  of  a  food  supply  will 
serve  to  maintain  a  majority  of  the  emerging  weevils  for  more  than 
three  weeks.  This  consideration  has  a  special  significance  in  southern 
Texas,  where  sprout  and  volunteer  cotton  usually  occur.  This  sub- 
ject will  be  further  considered  in  the  relation  of  hibernated  weevils 
to  food  supply. 

BEAKING   <>i    OBSERVATIONS   <»\    FED   AND  UNFED  WEEVILS  ON  THE 
POSSIBILITY  OF  A. VOIDING  DAMAGE  TO  COTTON  BY  LATE  PLANTING. 

One  of  the  most  import  ant  feat  ures  of  t  he  experiments  on  the  long- 
evity, with  and  without  food,  of  weevils  that  have  survived  the 
winter,  is  the  bearing  that  the  results  have  on  the  theory  of  late 
planting  of  cotton  to  avoid  damage.  This  theory  has  been  pro- 
pounded by  numerous  persons  ever  since  1895. 

In  the  series  of  experiments  with  unfed  weevils  4,600  individuals 
were  used  ;  in  the  series  with  fed  weevils  2,965.  The  unfed  series  is 
the  more  important  with  reference  to  late  planting,  The  maximum 
length  of  life  of  the  unfed  weevils  emerging  in  February,  1907,  was 


90 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


14  days;  the  average  6.9  days.  The  maximum  of  the  individuals 
emerging  in  March  was  51  days;  the  average  16.9  days.  For  the 
April-emerging  weevils  the  maximum  was  46  days;  the  average  21.2. 
For  the  May-emerging  weevils  the  maximum  33 ;  the  average  15.8  days. 
Of  the  June-emerging  weevils  maximum  12  days;  the  average  7.4.  It 
will  be  seen  that  even  in  such  an  abnormal  season  as  1907  weevils 
emerging  any  time  during  the  month  of  May  might  be  expected  to  live 
for  at  least  15  days  and  individuals  emerging  at  any  time  during  the 
month  of  June  to  live  for  more  than  7  days.  It  is  thus  clear  that  many 
weevils  emerging  in  May  would  survive  without  any  food  whatever 
until  considerably  after  the  middle  of  June  and  that  those  of  the  June 
emergence  would  survive  in  many  cases  beyond  the  first  of  July. 

It  is  important  to  note  that  a  considerable  percentage  of  the 
emerging  weevils  did  not  appear  until  late.  For  instance,  10.2  per 
cent  of  all  the  weevils  which  survived  at  Calvert  did  not  appear 
until  between  May  10  and  June  6.  At  Dallas  the  percentage  for  this 
period  was  7.5,  and  at  Victoria,  2.38. 

The  observations  on  the  longevity  of  the  fed  weevils  also  has  a  bear- 
ing on  late  planting,  since  there  is  always  some  volunteer  cotton 
around  seed  houses  and  elsewhere  that  will  be  found  by  the  weevils. 
The  maximum  length  of  life  of  the  fed  weevils  which  appeared  in 
February  was  47  days,  the  average  45  days;  of  March-appearing 
weevils  the  maximum  93  days,  average  45.5  days;  of  April-appearing 
weevils  maximum  82  days,  average  46.5  days;  of  May-appearing 
weevils  maximum  86  days,  average  55  days;  of  June-appearing 
weevils  maximum  46  days,  average  37.8  days. 

The  longevity  of  the  weevils  emerging  in  May  and  June  is  most 
important.  The  average  survival  of  55  days  in  one  case  and  the  37.8 
in  the  other  shows  that  with  such  food  as  can  easily  be  obtained,  at 
least  some  of  the  emerging  weevils  would  be  carried  over  until  far 
into  the  summer,  even  if  no  cotton  were  planted. 

The  records  just  referred  to  are,  of  course,  a  sufficient  refutation  of 
the  theory  that  the  weevil  could  be  " starved  out"  by  late  planting. 
It  has  been  proposed,  however,  that  the  number  of  weevils  surviving 
to  damage  late-planted  cotton  would  be  relatively  so  small  that  such 
cotton  would  have  a  better  chance  to  mature  a  crop  than  that  planted 
earlier.  In  order  to  test  this  matter  the  Bureau  of  Entomology  has 
conducted  practical  field  tests  in  which  cotton  has  been  planted 
about  the  10th  of  June.  In  one  season  four  of  these  experiments  were 
performed  in  parts  of  Texas  showing  distinct  climatic  features  and  one 
in  Louisiana  in  cooperation  with  1  lie  State  Crop  Pest  Commission.  In 
every  case  the  yield  was  cut  down  so  severely  by  the  weevils  that 
survived  the  prolonged  period  in  which  no  cotton  was  to  be  found 
thai  the  impossibility  of  producing  cotton  in  that  way  was  fully 
demonstrated. 


SEX   OF    WEEVILS   SURVIVING  HIBERNATION. 


91 


SEX  OF  WEEVILS  SURVIVING  HIBERNATION. 

We  found  it  possible  to  readily  and  accurately  recognize  male  and 
female  weevils  without  a  partial  dissection.  In  comparatively  few 
species  of  weevils  are  the  males  and  females  so  closely  similar  in  gen- 
eral external  character  as  in  the  case  of  the  Mexican  cotton  boll 
weevil.  It  was  found  that  size  depended  primarily  upon  the  food 
supply  of  the  larva  and  that  it  had  no  special  significance  in  regard 
to  sex,  although  it  appears  that  the  average  male  is  slightly  smaller 
than  the  average  female.  There  exists  a  rather  wide  variation  also 
in  coloration,  which  also  proved  to  depend  upon  food  supply  and 
age  lather  than  upon  sex. 

SECONDARY  SEXUAL  CHARACTERS. 


We  are  indebted  to  Dr.  A.  D.  Hopkins,  of  the  Bureau  of  Ento- 
mology, for  indicating  the  most  strongly  marked  points  of  difference 
in  the  secondary  sexual  characters  of  the  boll  weevil.     The  distinctive 


Fie.  0.    S«von«l;iry  sexual  t-hur.K  ters  of  Anthonnmus  gmmlis.    (After  Hopkins.) 

characters  (see  fig.  <))  are  found  upon  the  snout  and  upon  the  dorsal 
side  of  the  last  two  abdominal  segments,  which  are  normally  almost 
completely  hidden  by  the  wing  covers.  The  differences  are  subject  to 
some  variation  but  are  still  sufficiently  constant  to  enable  a  close 
observer  to  positively  separate  males  from  females  with  the  aid  of  a 
hand  lens.  Since  these  points  of  distinction  have  not  previously 
been  published  it  seems  advisable  to  include  them  here,  as  they  fur- 
nish the  basis  for  the  determinations  of  sex  which  follow. 

Female. — The  snout  of  the  female  is  slightly  longer  and  more 
slender  than  that  of  the  male.  It  usually  tapers  slightly  from  each 
end  toward  the  middle  when  viewed  from  above.  The  antennaa 
are  inserted  slightly  farther  from  the  tip  than  is  the  case  in  the  male. 
The  insertion  is  at  about  two-fifths  of  the  distance  from  the  tip  of 
the  snout  to  the  eyes.  As  a  rule  the  surface  of  the  snout  is  more 
smooth  and  shining  than  in  the  male.  A  slight  depression,  rather 
elongated  and  much  larger  than  any  of  the  other  punctures  upon  the 


92 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


snout,  occurs  between  the  bases  of  the  antenna?.  When  the  wing 
covers  and  wings  are  unfolded  the  abdomen  shows  seven  distinct 
dorsal  segments.  The  last  segment  visible  from  above  in  the  female 
is  called  the  propygidium.  In  the  female  this  covers  the  terminal 
segment  or  pygidium,  which  can  be  seen  only  from  the  sides. 

Male. — Snout  slightly  shorter,  thicker,  and  more  coarsely  punctured 
than  in  the  female.  The  depression  mentioned  in  the  female  is  lacking. 
The  antennae  are  inserted  at  practically  one-third  of  the  distance  from 
the  tip  of  the  snout  to  the  eyes.  The  sides  of  the  snout  are  very 
nearly  parallel.  In  the  abdomen  the  male  shows  eight  distinct  dorsal 
segments,  the  terminal  segment  (pygidium)  not  being  covered  by  the 
propygidium  as  is  the  case  in  the  female. 

In  general  practice  an  examination  of  the  snout  is  sufficient  to 
determine  the  sex  of  each  weevil. 

PROPORTION  OF  SEXES  SURVIVING  HIBERNATION. 

The  records  here  given  as  to  the  proportion  of  sexes  surviving 
hibernation  are  confined  to  determinations  of  sex  for  positively 
hibernated  adults. 

Table  XL VI. — Sex  of  iveevils  surviving  hibernation  in  Texas. 


Year. 


Locality. 


Male. 


Female. 


X  umber 
deter- 
mined. 

Percent- 
age of 
total  ex- 
amined. 

Number 
deter- 
mined. 

Percent- 
age of 
total  ex- 
amined. 

269 

60.7 

174 

39.3 

40 

60.0 

27 

40.0 

42 

66.7 

21 

33.3 

161 

55.0 

132 

45.0 

84 

59.6 

57 

40.4 

1,668 

54.2 

1,412 

45.8 

948 

53.0 

846 

47.0 

1,660 

61.3 

1,049 

38.7 

4,872 

a56.7 

3, 718 

a  43. 3 

1903.... 
1904.... 
1904.... 
1904.... 
1906.... 
1907.... 
1907.... 
1907.... 


Several  places . 

Calvert  

Victoria  

 do  

 do  

Dallas  

Calvert  

Victoria  


Total  and  average . 


a  Weighted  average. 

While  these  records  show  considerable  variation  in  the  proportion 
of  the  sexes  for  different  localities  and  during  different  seasons,  there 
is  a  uniformity  in  the  general  preponderance  of  males.  In  the  total 
of  9,000  weevils  examined  53.6  per  cent  were  males.  This  proportion 
corresponds  quite  closely  to  that  found  to  exist  among  weevils  enter- 
ing hibernation  (see  pp.  16-17).  It  is  evident,  therefore,  that  the  pre- 
ponderance of  males  in  the  spring  is  not  due  to  any  superior  power  of 
endurance  enabling  them  to  hibernate  more  successfully  than  fem;il<'s. 
Apparently  there  is  little,  if  any,  difference  in  respect  to  the  ability 
of  the  two  sexes  to  hibernate  successfully. 


RELATION  OF  HIBERNATED  WEEVILS  TO  FOOD  SUPPLY. 


93 


From  a  knowledge  of  the  habits  of  the  adults  it  appears  that  the 
preponderance  of  males  in  the  spring  i-s  favorable  provision  of  nature, 
making  it  more  certain  for  the  sexes  to  mate  and  to  insure  reproduc- 
tion. In  spite  of  a  number  of  attempts  to  obtain  a  definite  answer 
to  the  question  whether  it  is  absolutely  necessary  for  copulation  to 
occur  in  the  spring  before  females  can  reproduce,  this  point  has  not 
been  positively  settled.  There  are  indications,  however,  that  in  most, 
if  not  all,  cases  this  is  essential.  The  fact  that  mating  occasionally 
occurs  immediately  after  emergence  but  before  either  sex  has  fed  in 
the  spring  has  previously  been  noted.  I  nfert ilized  females  at  any 
season  of  the  year  deposit  nearly  all  of  their  eggs  upon  the  outside  of 
squares  or  bolls,  where  they  quickly  dry  up.  No  sign  of  partheno- 
genesis has  been  found.  The  meeting  of  males  and  females  is  to  a 
large  degree  accidental,  and  during  a  season  when  weevils  are  com- 
paratively  scarce  it  is  likely  that  in  very  many  cases  the  sexes  fail  to 
conic  together  or  the  meeting  may  be  delayed  for  a  considerable 
period. 

Experiments  have  shown  that  the  male  weevils  do  not  actively  seek 
the  females.  They  seem  t<>  recognize  their  presence  through  a  dis- 
tance of  hardly  more  than  an  inch.  The  meeting  of  the  sexes  depends 
therefore  largely  upon  their  coming  into  close  proximity  upon  a  cot- 
ton plant.  Since  the  males  are  less  active  in  their  movement  than  are 
the  females,  the  value  of  the  existence  of  a  majority  of  males  be- 
comes apparent.  The  larger  number  of  males  and  the  more  active 
habits  of  the  females  serve  t<»  increase  the  chances  for  the  meeting 
of  the  sexes  in  the  spring  without  materially  decreasing  the  power 
of  multiplication  of  t  he  species. 

RELATION  OF  HIBERNATED  WEEVILS  TO  FOOD  SUPPLY. 

The  iclation  of  hibernated  weevils  to  food  supply  is  an  important 
subject ,  since  the  reproduction  and  multiplication  of  the  species  de- 
pend primarily  upon  this  point.  As  has  been  shown  in  numerous 
places  the  emergence  period  of  the  weevil  practically  coincides  with 
the  average  period  in  the  planting  of  cotton.  The  long  duration  of 
emergence  makes  it  practically  impossible  to  secure  the  planting  of 
the  entire  crop  either  earlier  or  later  than  the  emergence  period  of  the 
weevil.  It  has  been  found  both  from  the  study  of  the  weevil  and  from 
large-scale  experiments  in  the  culture  of  cotton  that  during  nearly 
every  season  there  is  a  decided  advantage  in  planting  the  crop  as 
early  as  soil  and  climatic  conditions  may  permit.  Too  much  empha- 
sis can  not  be  placed  upon  the  fact  that,  at  whatever  time  the  cotton 
in  a  locality  may  he  planted,  there  will  be  a  decided  ad'vant age  in  hav- 
ing it  all  planted  at  as  near  a  uniform  date  as  is  possible.  It  is  obvious 
that  this  will  entirely  prevent  the  development  of  weevils  until  prac- 
tically all  of  the  crop  begins  fruiting.    In  this  way  the  fruiting  of  the 


94 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


plant  may  take  place  most  rapidly  during  the  period  of  development 
of  the  first  and  second  generations  of  weevils. 

Early  planted  fields,  although  they  may  serve  to  attract,  in  some 
small  degree,  the  weevils  from  surrounding  fields,  will  almost  invariably 
produce  larger  yields  than  later  planted  fields  in  the  same  locality. 
The  reason  for  this  is,  primarily,  the  longer  period  which  intervenes 
between  the  beginning  of  setting  fruit  with  its  coincident  reproduction 
of  weevils  and  the  time  when  maximum  infestation  of  the  field  occurs. 
Comparatively  few  weevils  appear  to  move  from  one  field  of  cotton  to 
another  until  after  maximum  infestation  takes  place. 

Repeated  experiments  in  deferring  the  planting  time  of  cotton  have 
invariably  resulted  in  small  and  comparatively  unprofitable  crops. 

Extended  observations  made  during  the  spring  of  1906  showed  that 
volunteer a  cotton  occurred  very  commonly  in  fields  and  yards,  along 
roadsides,  and  around  ginneries  and  seed  houses  in  every  one  of  the 
seventeen  localities  examined  about  the  middle  of  May,  representing 
territory  then  infested  by  the  weevil  and  also  extending  outside  the  in- 
fested territory  into  Mississippi,  Arkansas,  and  Tennessee.  This  makes 
it  practically  certain  that  volunteer a  cotton  occurs  everywhere 
throughout  the  cotton-growing  area,  and  it  may  therefore  have  con- 
siderable significance  in  supplying  emerged  weevils  with  their  first 
food  in  spring. 

Extensive  examinations  have  also  shown  that  sprout a  cotton  com- 
monly occurs  throughout  the  southern  half  of  the  weevil-infested  area 
in  Texas  during  the  average  season.  As  a  rule  the  development  of 
this  takes  place  several  weeks  in  advance  of  the  average  planted  cot- 
ton, and  it  becomes  therefore  a  very  important  factor  in  maintaining 
hibernated  weevils  and  in  the  development  of  their  first  progeny. 
Although  attention  has  repeatedly  been  called  to  this  fact,  large  quan- 
tities of  sprout  cotton  are  still  allowed  to  grow  unchecked.  It  is 
doubtful  whether  it  is  advisable  to  cultivate  this  even  where  it 
amounts  to  half  a  stand.  Wherever  scattering  plants  occur  in  a  field 
of  planted  cotton  they  should  certainly  be  chopped  out  as  quickly  as 
they  occur.  The  profit  to  be  derived  from  them  is  nothing  when  com- 
pared with  the  groat  damage  which  their  presence  may  inflict  upon 
the  remainder  of  the  crop  through  providing  the  earliest  opportunities 
for  the  reproduction  and  multiplication  of  the  weevils. 

«  The  term  "volunteer"  is  restricted  to  that  class  of  cotton  coming  from  the  acci- 
dentally scattered  seed  of  a  preceding  crop.  Sprout  cotton,  also  called  stubble  or 
seppa  cotton,  is  a  sprout  growth  from  old  cotton  roots  occurring  during  the  winter  or 
subsequent  spring. 


SUMMARY  AND  CONCLUSIONS. 


95 


SUMMARY  AND  CONCLUSIONS. 

Hibernation  is  the  term  used  to  designate  those  phases  in  the  life 
and  seasonal  history  of  the  boll  weevil  (or  of  any  other  animal  or 
plant)  which  are  concerned  with  its  existence  through  the  winter  and 
the  manner  in  which  the  species  is  protected  or  maintained  in  passing 
from  one  season  to  the  next.  Food,  climatic,  and  shelter  conditions 
are  the  principal  factors  concerned  in  hibernation. 

Food  conditions  in  the  fall  govern  largely  the  abundance  of  indi- 
viduals which  may  enter  hibernation  and  therefore  affect  the  abun- 
dance of  the  species  in  the  following  spring,  since  climatic  and  shelter 
conditions  govern  largely  the  proportion  of  the  hibernating  individ- 
uals which  may  survive. 

A  large  majority  of  the  weevils  developed  in  a  field  during  the 
season  are  produced  from  squares. 

Weevils  becoming  adult  comparatively  late  in  the  season  are  more 
likely  to  survive  hibernation  than  are  those  which  have  been  active 
for  a  number  of  weeks  before  the  time  arrived  for  them  to  hibernate 
successfully. 

It  is  possible  that  offspring  of  each  of  the  four  or  five  generations 
which  are  produced  on  the  average  may  survive  to  enter  hibernation. 

No  "top  crop''  can  reasonably  be  expected  within  the  weevil- 
infest  ed  area. 

All  stages  of  the  weevil  may  enter  hibernation  and  under  excep- 
tionally fa  vorable  cliniat  ic  conditions  Larvae  which  are  more  than  half 
grown  may  complete  t  heir  development  if  in  bolls  and  become  mature 
dining  the  hibernation  period.  Immature  stages  in  squares  rarely 
survive.  Nearly  all  of  the  weevils  surviving  were  adult  before  the 
beginning  of  the  hibernation  period. 

The  destruction  of  stalks  in  the  fall,  as  long  as  possible  before  the 
normal  hibernation  time,  is  t  he  most  economical  and  effect Lve  method 
known  for  reducing  the  number  of  weevils  entering  hibernation. 

u Entrance  into  hibernation  "  denotes  the  beginning  of  t  he  generally 
inactive  period,  but  it  does  not  necessarily  imply  a  change  of  posit  ion 
for  thi  individuals  involved.  For  the  species  and  often  also  for  the 
individual  it  is  a  gradual  process  depending  primarily  upon  tempera- 
ture conditions.  The  duration  of  the  entrance  period  for  the  species 
depends  upon  the  severity  of  the  drop  in  temperature  below  about 
43  degrees  of  mean  average  temperature.  This  period  usually  occurs 
coincidently  with  the  first  killing  frosts  and  extends  through  a  period 
of  about  twenty-five  days. 

From  close  examination  of  1,750  weevils  it  seems  that  about  60 
per  cent  of  those  entering  hibernation  are  males. 

The  number  of  weevils  per  acre  or  per  plant  which  may  enter  hiber- 
nation depends  especially  upon  preceding  climatic  and  food  conditions 


96 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


and  has  been  found  to  vary  in  different  seasons  and  localities,  occa- 
sionally being  as  high  as  50,000  weevils  per  acre,  or  an  average  of  from 
7  to  10  weevils  per  plant.  An  average  of  the  results  in  17  of  the 
most  carefully  studied  fields  shows  8,552  weevils  per  acre,  or  slightly 
more  than  1  weevil  per  plant. 

The  proportion  between  the  numbers  of  weevils  hibernating  on  the 
stalks  and  among  rubbish  scattered  on  the  surface  of  the  ground 
changes  as  the  season  advances,  the  number  on  the  stalks  decreasing. 

Great  mortality  occurs  soon  after  the  weevils  enter  hibernation, 
especially  among  those  upon  the  surface  of  the  ground. 

Hibernation  usually  takes  place  as  the  mean  average  temperature 
falls  below  55  degrees  and  may  remain  complete  until  the  mean 
temperature  rises  above  60  degrees. 

Weevils  may  avail  themselves  of  almost  any  kind  of  shelter,  and 
the  favorable  character  of  the  shelter  in  relation  to  prevailing  cli- 
matic conditions  will  influence  the  percentage  of  survival.  Many 
pass  the  winter  sheltered  by  the  old  bolls  that  remain  hanging  upon 
the  stalks.  The  percentage  of  survival  in  bolls  decreases  generally 
from  southern  to  northern  Texas.  Bolls  are  frequently  so  important 
a  factor  in  shielding  weevils  from  one  season  to  another  that  it  is 
advisable  to  destroy  them  as  a  regular  practice  even  in  northern 
Texas. 

Exceptionally  cold  and  wet  winter  weather  is  most  unfavorable  for 
weevil  survival.  The  destruction  of  possible  shelter  through  clean 
culture  in  the  fall  is  an  effective  way  of  reducing  weevil  injury  to  the 
following  crop.  The  shelter  to  be  found  in  timber  fringes  around 
cotton  fields  is  much  more  difficult  to  remove  or  control  than  is  that 
within  the  fields.  The  importance  of  such  unavoidable  conditions 
may  be  minimized  by  judicious  cleaning  up  and  by  rotation  of  crops. 

Occasionally  weevils  may  survive  in  stored  cotton  seed  and  be  dis- 
tributed along  with  it  at  planting  time.  This  fact  justifies  the  main- 
tenance of  quarantine  regulations  against  the  free  movement  from 
infested  to  uninfested  territory  of  cotton  seed  and  closely  related 
cotton  products  which  are  apt  to  shelter  weevils. 

Most  of  the  information  obtained  in  regard  to  the  hibernation  of 
the  weevil  has  resulted  from  cage  experiments  in  which  the  influential 
conditions  could  be  separated  and  to  some  degree  brought  under 
control. 

During  the  winter  of  1902-3,  at  Victoria,  Tex.,  in  the  small-cage 
experiments  with  356  weevils,  an  average  of  about  11  per  cent  sur- 
vived. During  the  following  season,  also  at  Victoria,  among  400 
weevils  but  one-fourth  of  1  per  cent  survived.  During  the  winter  of 
L904-5  larger  numbers  of  weevils  were  under  observation  at  ek&h  of 
six  Localities  ranging  from  the  southern  to  the  northern  portions  of 


SUMMARY  AND  CONCLUSIONS. 


97 


the  infest ed  area.  This  was  the  season  of  most  exceptional  rainfall 
and  cold,  and  it  was  not  surprising  that  no  weevils  survived  in  the 
Cage  tests  except  at  Victoria,  which  was  the  southernmost  point 
of  experiment .  An  average  for  tlie  six  localities  shows  a  survival  of 
IflSfl  than  two-thirds  of '1  per  cent.  In  the  small-cage  work  of  1905-6 
there  was  an  average  survival  of  1.3  per  cent,  and  practically  all  of 
this  occurred  in  the  outdoor  cages. 

The  most  important  work  done  in  1905-6  was  in  a  large  cage  at 
Keatchie.  La.!  where  25. MM)  weevils  were  placed  in  IS  compartment s, 
The  survival  in  this  cage  was  2.82  per  cent,  and  the  emergence . oc- 
curred between  March  22  and  June  28,  1906.  The  cages  having 
nearest  to  the  ordinary  Held  conditions  with  poor  cultivation  gave 
the  Largest  percentage  of  successful  hibernation.  A  study  of  the 
emergence  and  temperature  records  for  similar  experiments  at  Dallas, 
Tex.,  and  Keatchie,  La.,  shows  t  hat  at  t  he  former  place  approximately 
50  per  cent  of  the  emergence  occurred  while  the  temperature  ranged 
between  58  and  6S  degrees,  while  at  the  latter  place  one-half  of  the 
total  emergence  took  place  while  the  temperature  ranged  between 
about  65  and  75  degrees.  Very  few  weevils  emerged  while  the  tem- 
perature was  below  57  degrees. 

There  is  an  optimum  period  for  entrance  into  hibernation,  and 
\veevi!>  entering  during  this  period  have  a  considerably  better  chance 
of  surviving  than  do  those  which  enter  either  earlier  or  later.  If" 
hibernal  ion  i>  begun  earlier  than  this  optimum  period,  it  is  likely  that 
emergence  will  be  completed  earlier  during  the  following  season,  and 
also  if  entrance  occurs  later  than  this  period  it  is  likely  that  emer- 
gence will  begin  unusually  early  in  the  following  spring. 

Variation  in  the  period  of  entrance  into  hibernation  and  the  dif- 
ference in  the  nature  of  the  shelter  secured  by  the  weevils  may  rea- 
sonably account  for  the  variations  found  in  the  amount  of  accumu- 
lated effective  temperature  required  to  produce  complete  emergence 
in  the  spring. 

Weevils  emerging  earlier  in  the  season  survived  for  a  longer  period 
than  did  those  which  emerged  after  the  middle  of  the  emergence 
period.  It  is  a  common  occurrence  for  weevils  to  leave  their  winter 
quarters  upon  warm  days  in  spring,  returning  again  to  a  condition 
of  inactivity  for  a  period  of  several  days  or  even  weeks.  Disappear- 
ance and  reappearance  in  the  case  of  plainly  marked  individuals  has 
been  observed  to  occur  as  many  as  eight  times,  and  a  maximum 
period  of  forty-three  days  between  appearances  has  been  recorded. 
These  facts  argue  very  strongly  indeed  against  the  proposition  which 
is  sometimes  made  by  those  who  are  not  thoroughly  familiar  with  the 
habits  of  the  weevil,  to  starve  the  emerged  weevils  by  deferring  the 
planting  of  cotton  in  the  spring.  Two  lots  of  20  and  8  weevils  sur- 
90317— Bull.  77—09  7 


98 


HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 


vived  for  an  average  of  thirty  and  sixty  days,  respectively,  after  emer- 
gence without  a  particle  of  green  food  from  the  time  of  their  entrance 
into  hibernation  to  the  time  of  their  death.  Other  tests  show  similar 
results. 

The  hibernation  experiments  of  1906-7  consisted  of  large-cage 
work  in  three  localities  representing  the  northern,  central,  and 
southern  portions  of  the  infested  area.  Each  cage  inclosed  10  sepa- 
rate experiments  and  the  comparisons  made  possible  by  the  three 
locations,  the  different  shelter  conditions,  and  the  different  dates  of 
instituting  the  experiments  furnish  the  basis  for  the  most  complete 
and  significant  work  which  has  been  done  with  the  hibernation  of  the 
weevil. 

Owing  to  the  exceptional  mildness  of  this  season,  complete  hiber- 
nation did  not  occur  at  any  time  during  the  winter  in  any  part  of 
Texas.  Emergence  began  during  the  last  week  or  ten  days  of  Feb- 
ruary, 1907.  At  Dallas  7.8,  at  Calvert  10.5,  and  at  Victoria  27.7  per 
cent  of  the  total  numbers  of  weevils  placed  in  the  cages  were  counted 
as  being  active  at  some  time  during  the  winter  season  when  they 
should  normally  have  all  been  in  complete  hibernation.  About  13 
per  cent  of  the  adult  weevils  buried  with  a  lot  of  bolls  under  2  inches 
of  heavy  ,  black  soil  escaped  and  were  found  upon  the  cage  screen  dur- 
ing the  next  few  days.  Weevils  were  active  in  the  field  as  well  as  in 
the  cages  during  this  winter.  The  period  of  greatest  emergence  oc- 
curred during  the  latter  part  of  March,  which  was  undoubtedly  from 
four  to  six  weeks  earlier  than  is  usual.  Succeeding  low  temperatures 
served  to  prolong  the  period  of  emergence  until  the  1st  of  July.  In 
the  three  localities  under  observation  an  average  of  11.5  per  cent  of 
the  75,000  weevils  placed  in  the  experiments  survived  and  emerged 
in  the  spring  of  1907. 

Grouping  the  experiments  in  the  three  localities  according  to  the 
dates  of  installation  of  the  weevils  and  averaging  the  percentages  of 
survival  in  each  group,  it  appears  that  there  was  a  steady  increase  in 
this  percentage  upon  succeeding  dates  after  the  middle  of  October, 
when  the  experiments  were  started,  to  the  end  of  November,  when 
the  last  weevils  were  placed  in  the  cages.  This  increase  is  so  nearly 
regular  as  to  prove  conclusively  that  the  date  at  which  weevils  are 
deprived  of  food  in  the  fall,  in  its  relation  to  the  most  favorable  period 
for  entrance  into  hibernation,  has  a  most  vital  influence  upon  the 
prospect  for  survival.  Among  the  weevils  started  October  14  but 
3.14  per  cent  survived,  while  among  those  started  just  one  month 
later  an  average  of  19.67  per  cent  survived.  These  results  prove 
absolutely  the  advisability  of  destroying  the  food  supply  of  the 
weevils  at  leasl  three  weeks  before  the  usual  time  for  the  first  frosts 
to  occur,  and  they  show  very  plainly  just  why  such  a  practice  is  the 


SUMMARY  AND  CONCLUSIONS. 


99 


most  effective  method  yet  found  for  reducing  the  number  of  weevils 
that  may  survive  the  winter  to  attack  the  crop  of  the  following  sea- 
son. This  portion  of  the  bulletin,  especially,  should  be  carefully 
studied  in  detail. 

The  survival  in  the  various  sections  of  the  cages  in  the  three  locali- 
ties ranged  from  1.89  to  31.34  per  cent.  The  average  survival  in 
each  of  the  localities  was  as  follows:  Calvert,  9.49  per  cent;  Dallas, 
11.22  per  cent;  Victoria,  13.47  per  cent. 

At  Dallas  the  largest  percentage  of  survival  occurred  in  a  section 
of  the  cage  having  an  abundance  of  fallen  leaves,  in  which  the  weevils 
were  placed  on  November  15  and  with  the  cotton  stalks  left  standing. 
The  smallest  survival  occurred  in  a  section  having  fully  as  favorable 
shelter  conditions  but  in  which  the  weevils  were  placed  on  October  13 
and  left  without  any  food  from  October  15. 

At  Victoria  the  largest  survival  occurred  among  weevils  started  on 
November  (\  without  food  in  the  Bectiorj  provided  with  Spanish  moss 
and  bark. 

The  winter  was  too  mild  to  furnish  any  comparative  test  of  the 
favombleness  of  various  shelter  conditions,  but  in  general  it  appears 
that  fallen  leaves,  Spanish  moss,  and  a  heavy  growth  of  grass  are 
most  favorable  to  the  weevils  wherever  they  may  occur. 

Temperature  conditions  were  practically  normal  during  November, 
l'JOli,  and  the  most  favorable  time  for  entrance  into  hibernation  was 
between  November  l'J  and  1  5  at  Dallas  and  slightly  later  at  the 
more  southern  points. 

In  each  locality  the  maximum  longevity  was  shown  by  males,  and 
the  average  duration  of  life  of  that  sex  was  also  slightly  in  excess  of 
that  of  females.  The  average  survival  of  all  weevils  kept  without 
food  was  about  ten  days,  and  a  considerable  number  lived  to  between 
six  and  twelve  weeks  after  emergence.  The  maximum  survival  for 
any  unfed  weevil  w  as  ninety  days.  Obviously  there  is  no  chance  to 
starve  out  all  weevils  by  any  possible  delay  in  planting. 

Among  the  fed  weevils  the  longest-lived  was  also  a  male  which 
was  active  for  one  hundred  and  thirty  days  after  its  emergence. 
The  longest-lived  female  was  active  for  one  hundred  and  eighteen 
days.  The  average  active  life  for  all  fed  weevils  was  25.5  (bus  after 
emergence.  Practically  one-half  of  all  fed  weevils  lived  for  more 
than  six  weeks  in  the  spring. 

The  sex  was  determined  for  more  than  8,500  weevils  which  had 
survived  the  winter,  and  it  was  found  that  56.7  per  cent  of  these  were 
males.  There  is  an  invariable  preponderance  of  males  both  in  the 
fall  upon  entering  hibernation  and  in  the  spring  upon  emergence 
therefrom. 

Reproduction  can  not  begin  until  the  first  squares  become  at  least 
half  grown.    At  whatever  date  cotton  may  be  planted  in  a  locality, 


100  HIBERNATION  OF  THE  COTTON  BOLL  WEEVIL. 

there  is  a  decided  advantage  in  having  it  all  planted  at  as  nearly  a 
uniform  date  as  is  possible.  As  a  rule  early-planted  fields  yield  better 
than  do  those  planted  later,  but  with  similar  conditions  of  seed,  soil, 
and  cultivation.  All  volunteer  and  sprout  cotton  developing  in 
advance  of  the  main  crop  should  be  destroyed  before  it  forms  squares, 
since  otherwise  it  may  furnish  the  weevils  with  opportunities  for 
reproduction  for  some  time  before  squares  become  common  and 
thereby  unnecessarily,  early  in  the  season,  increase  their  numbers 
and  the  resultant  injury  to  the  main  crop. 


O 


